First Outings with Tyranids

I finally fielded my happy, happy little swarm of gribbles, and managed to eke out a couple of wins. I did not think to take my crappy little camera, and today, well, I'm still a weeeeee bit out of it on antibiotics. (Allergy season startup + sinus infection = floored raptor, add in the scorched-earth antiobiotics and I was motionless from about noon Wednesday to 4PM Thursday, and fading in and out of delightful madness today).

So, the list I ran with:
Tyranid Prime w/ 2x Boneswords
3x2 Hive Guard
2x10 Termagants
2 Tervigons w/ Toxin, Adrenal, Catalyst
6 Shrikes w/ whip/sword
2x18 Gargoyles w/ Toxin, Adrenal
2x Tyrannofex w/ Cluster Spines, Rupture Cannon, default thorax swarm

Played two objective games; one against Black Templar double-raiders and one against Tyranids.

Brother-Captain w/ Hood
Emperor's Chump w/ Preferred Enemy vow
2x 5-man assault termie squads (4 claws, 1 hammer/shield)
2x8-9 fellows in Rhinos w/ melta, fist
2x5 man las/plas
2x mm/hf speeders

Tyranid List:

Swarmlord w/ 3 Tyrant Guard
3 Zoanthropes
2 Hive Guard
2 large squads of Hormagaunts (~20)
2 small squads of Termagants (~10)
4 Warriors w/ Swords, Devourerers
3 Raveners
Tyrannofex
Trygon Prime

General Tyranid Thoughts
On Land Raiders
Frankly, I figured I'd shoot his support before I shot his raiders. This proved to be wise, as I had some good rolls and managed to total his Rhinos and ruin his speeders in 1-2 turns. (Well, he made the mistake of leaving a rhino in range of Hive Guard on turn one, so it got maimed, and the Tyrannos accounted for the other one and a speeder).

You will have to give yourself over to the idea that you're gonna be doing one of three things to kill a Land Raider:
1) Shoot it with a Zoanthrope
2) Shoot it with a Tyrannofex
3) Punch it repeatedly with a monstrous creature

The raiders were a pain, in part because even after one squad of termies broke from shooting and ran, he slapped one on my objective. I won the game against the Templars because it went into seven turns and I managed to kill the Raiders on turns six and seven. Admittedly, that was some pretty poor Tyrannofex shooting there, and then a Tervigon wandered over and punched one in the explosives.

Hive Guard
I haven't run the new Zoeys yet, but with everyone and their dog packing some kind of psychic defense, I have to admit I like the reliability of two S8 shots at BS4. These things are happy to maim up lighter mech, and against any T4 multi-wound bug? Ouch. My tyranid opponent made the mistake of leaving Warriors in the open for a turn, and they paid for it. They're also good for taking out Zoeys, or at least forcing instant-death saves.

Tyrannofexes
Now, I know there have been some critics of the t-fexes, but I have to say they have a place. Why? Several reasons.

1) S10 shots
2) 48"
3) T6, 6 wounds, 2+ armor save

S10 means it CAN threaten AV14, but against lighter armor? Two shots at BS3 mean that 25% of the time you'll see 0 hits, 25% of the time you'll see 2 hits, and 50% of the time you'll see a hit. Against Rhinos, Landspeeders, and even AV12 (other than Eldar skimmers...) you're probably gonna get a pen. Seriously, it's some decent firepower.

48 inches means you can shoot pretty much from the start. Considering that you NEED all the shooting you can get to stop/slow mech, this means there's nowhere to really run.

The durability means that against shooting, either the opponent brought a crap-ton of lascannons or he's not going to bother engaging your Tyrannofex at range. He'll either melta it, throw powerfists/thunder hammers at it, or ignore it. That means you get to shoot, and you'd BETTER screen the bloody thing.

As an added bonus, the Cluster Spines and flamer templates are nice point-defense goodies. I lost the Gaunt screen to a Hormagaunt charge in game two, and dealt with this by burning half the brood (bad consolidation roll) with the t-fex, and gunning the rest down with fleshborers.

Bottom line? It's a solid performer, but it is for a shooty-heavy build.

On Gargoyles and Shrikes
I won't lie; I was a little worried about taking these guys. I like the gargoyle sculpt, and I figured that the Shrikes would provide some punch/synapse. It gave the build some speed and a rapid-response element, which turned out to be useful.

The down side? Hello, traffic jam. Thank god I didn't see a crap-ton of templates or such early on, as that's just a lot to deploy. Additionally, that's a LOT of ground to cover; Gargoyles will be taking dangerous terrain tests, but you should be able to avoid moving through terrain for the assault.

Shrikes? Mmm, power weapon love. The whip is absolutely a keeper. Instant death is nice and all, but robbing the enemy of the initative is big. Going into cover? It's 4th-ed frags. Going into a faster creature? Slap one in base-to-base contact. Shank with power weapons. Enjoy.

The gargoyles help in a charge, but honestly you need a little more punch to take stuff down. They DID manage to drag down a Tyrannofex, but that was after knocking off one wound with massed small-arms fire, then going poison + to-hit wounds all over it. Granted, it TOOK several turns, but it stopped the big brute.

Still, there's nothing like watching 10-20 of them around a target, and seeing a few heads and powerfists above the mass. It made it totally worthwhile.

The Swarmlord
...what a beast. Frankly, as 'nids, I don't have enough high-AP shooting to reliably drop wounds on him. Ok, we have plenty of S8-10 fire available, but sometimes it was going elsewhere and we've all played Space Marine players with hot dice before, right? This guy took some serious dog-piling to drop. I managed to KO one guard before it got there. Then, I threw Termagants, Gargoyles, and Shrikes at it, and drug it down over a couple of turns. It managed to kill a heap of gargoyles, termagants, and all but one Shrike (which was busy holding it down).

Lesson learned? GET POISON ON THE BLOODY SHRIKES. Would have made it SO MUCH EASIER.

Still, all things considered, the Swarmlord is a nasty foe for bugs to deal with. You pretty much have to drown 'im in poison weapons and expect to take heavy casualties. As well it should be, for 280+ points of the army...

Tervigons
Or, 'we have reinforcements!' Anyone who's pulled off the Kroot Shield knows what I'm talking about. Round one, I managed to spawn one brood each, and game two I managed a total of four broods. Honestly, it's enough. You get into some serious traffic-direction issues in the backfield...

On the other hand, there's a LOT of fun to be had with Catalyst. Fun uses for Feel No Pain include:

1) Making Termagants last
2) Making Gargoyles last in the open
3) Keeping Shrikes alive against small arms
4) Softening the impact of 'No Retreat!'

Number four was the big one. There are some furballs you're just not gonna win quickly. You're going to have to wear the enemy down, and the problem is lsoing troops with 'No Retreat'. Well, now you lose half of them. If the enemy doesn't have power weapons or the like, then you can last. Plus, your piddly little T3 6+ save fellows can actually endure a little more abuse. Why, you're about as tough as an Eldar Aspect Warrior!

General Tyranid Thoughts
Traffic direction is an issue. This army's deploying something like 60-70 figs off the bat. No tanks. The only thing that relocates more than 6" a turn are the flyers. With Tervigons, you're dropping even MORE of them on the table.

The games have been close so far, and I think that might be partially due to the build, and partially due to getting used to a new playstyle. This current build reminds me of my Tau, except I can actually fistfight in a pinch.

Mild Apology
I'm still a tad bit loopy. This crud actually started ramping up around last Sunday, but didn't hit in full force 'til Wednesday. There'll be some more lucid-sounding points eventually.

Non-Basic Army Building: Psychological Warfare

I file psychological warfare as a non-basic part of army building because it's in your head, and in your opponent's head. As such, it's harder to guess what will work on any given individual. The short version of psychological warfare: the percieved danger of a unit causes an opponent to deviate from their battle plan.

Note this is the percieved danger, not the actual danger.

Psychological warfare is, simply put, about screwing with the other guy's head. At the moment, the best I can think of is to offer some examples of psychological warfare units, and how/why they are percieved as such. Note that this is not an exhaustive list of psychological warfare units; it's just an example of some and a few thoughts on why they qualify.

The Doom of Malant'ai

Well, let's go right on ahead and start with the one everyone's talking about. See, part of its impact is the fact that everyone seems to be talking about it. It's all 'OH MY GOD! IT CAN GET 10 WOUNDS AND THROW OUT AN S10 AP1 BLAST! IT CAN KILL 10,332.77721 INFANTRY IN ONE PHASE!' And then there's the whole rules debate about whether or not infantry in transports are effected by the whole 'psychic vampire' deal.

Now why, exactly, do people worry about it? Here's what I can think of:

1) On a good drop, it can potentially effect several infantry units

2) It can potentially force morale checks/retreats on said infantry units

3) It turns around, has 7-10 wounds to its name, and applies a thermonuclear psychic blast to something important

4) Oh, and it also arrives via drop pod, so there are fewer issues with mishaps

So, we've established (in people's minds) that it can potentially ruin your day single-handedly. Ok, now let's pierce the psychological veil:

1) the average roll on 3d6 is 10-11; most units have ld 8-10. This is 1-3 casualties. Big whoop.

2) S8 doesn't care how many wounds you have after you fail a save

3) Can't shoot that psychic blast if you're in assault

4) Psychic hoods, etc. still stop the Cataclysm

Now, the Doom probably WILL kill some infantry (if it hits 'em in transports), but unless you really cluster up and give the doom a sweet spot to land in, it'll kill a few, and hopefully your army has some S8 around to deal with the problem. Can you hit it with three S8 wounds? Then you can probably solve the problem. Or, can your army take out a marine squad in a turn? Then the worst the Doom did was absorb fire.

Guardsman Marbo

Marbo is, in my mind, a bit more credible of a threat than the Doom. Marbo is a mere 65 points for a guy with Stealth that appears where he wants to. Once there, he has a nasty pistol, a demo charge, and poisoned melee attacks.

Why is he scary?

He can't be within 1" of the enemy. He is one infantry unit. It is very easy to leave a hole (as he only needs a 2inch + 20mm hole to appear in) he can inhabit. Then, he chucks a demo charge at something expensive.

Rambo basically makes you ask 'did I deploy in such a manner as to deny the enemy a demo charge shot into the rear of a vehicle?

Basically, he's enough of a bargain (in non KP missions, anyway) at 65 points to make the other guy deploy a little more carefully.

It's nastier against armies that have multi-wound T4 creatures, as S8 can insta-kill priority targets like Crisis Suits, Tyranid Warriors, and Zoanthropes just to name a few. It also can harm vehicles, especially if you tag them from behind.

On the other hand, once he chucks the demo charge, Rambo is not THAT frightening. He'll throw out pistol shots, or try to stab something, but you can usually turn around and just shoot him down or assault him. All he does after the demo charge is beg for bullets and a gruesome death.

Indirect-Fire Artillery

This is actually a category as opposed to a specific unit. Basically, something like a Whirlwind or Basilisk sits back and chucks explosives at you, and you can't shoot it back (unless you have ordnance of your own). This is frustrating because it feels 'unfair'; nevermind that your opponent paid points for it normally. It's shooting YOU, but YOU can't SHOOT IT BACK! It's frustrating for some folks.

Outflanking Troops

But, but, what happens if they're suddenly on your flanks? The scare value of outflankers depends on the outflankers and what they can actually do when they get there. You're gambling that you'll get your troops on the right side (66% chance, or the same as a power armor save before any re-rolls) at the right turn (...good luck computing those odds) and they'll be able to do something (which is rather up to your opponent).

If you're outflanking a smaller unit or only 1-2 selections, it's not a credible threat. If you outflank too much, you risk diluting your main forces. I mean, you COULD outflank a Land Raider full of Terminators*, but what happens when it shows up on turn 5 and 600 points of your army did precious little?

It's a gamble, but it's one I honestly don't think much of. However, that's me.

Psychological Warfare versus Legitimately Deadly Stuff

Some units draw fire because of their percieved danger. Other units draw fire because they actually ARE that frightening. Here are some examples of units that draw a heap of fire just because of the damage they can reliably do to your army, and they'll rarely last a match.

Space Marine Land Speeders w/ Multi-melta, heavy flamer

Did you bring tanks? It can nuke 'em. Did you bring non-power-armor infantry? We can roast 'em. It's an AV10 platform that's in your face, threatening your assets with death on turn 2. The only armies that don't abjectly worry about them are those that tend to 'spam' stuff like razorbacks or chimeras. Anyone relying on heftier tanks or camping infantry have GOT to pay attention to these things, or risk losing expensive tanks or swathes of infantry.

Tau Piranhas

They have BS4 meltaguns. They are fast. They can get in your way. They are AV11, so you HAVE to use anti-tank weapons on them. Oh, and did I mention they'll block you and/or kill your expensive stuff if you don't handle them? They may not always kill stuff, but they CAN impede progress and buy time for the Tau player, which is well worth it.

Eldar Fire Dragons

How do 5 meltaguns at point blank strike that Land Raider, monstrous creature, T4 multi-wound unit, etc.? I think the answer is 'very nicely' if you're Eldar, and 'OW!' if you're not. Fire dragons draw so much fire because they really ARE that good (and cost-effective) at killing stuff. They're a legitimate threat to any armor short of a full-on infantry horde.

The Real Perk of Psychological Warfare

The real goal of psychological warfare is to make the enemy make a mistake. You're bringing a unit whose percieved danger is out of proportion to their actual danger, or at least you hope that's how the other guy views it. Is it viable? The answer is actually the two most powerful words in the English language: 'It Depends.' It depends on the unit you're calling on to do this task, and on how the other guy percieves it.

That's why I consider psychological warfare a gamble. It will work on some people some of the time, and you're hoping that's enough.

*Provided you take Khan, and take the Land Raider as a dedicated transport.

Painted Tyrannofex

So, I finished painting this monstrous, walking gun-beast thing. I've constructed a white backdrop for pictures, and attempted to locate a better camera than the one I've sort of been given. (There was a reason it was a 'gift'...)

Enjoy. The thing was fun to convert, though my paint scheme came out a bit bluer than I'd thought, but I kinda like it. at any rate, I don't feel like stripping this one and 20 Termagants.

Army Building 101: Essential Capabilities

This article springboards off of my posts on evaluating units honestly and making tradeoffs. This is a little basic, but you need to bring the tools to do three basic things:

1) Hold Objectives
2) Stop Enemy Armor
3) Kill Enemy Troops

You need to hold objectives in 2/3 of the games, but make sure that you don't actually hurt yourself when it comes to killing the other guy. When it comes to stopping the other guy, you want to be able to stop vehicles AND enemy troopers.

1) Controlling Objectives
Objective games break up into two categories: 2 objectives, or 3+ objectives. The number of objectives changes the way you play, but not necessarily how you build. Controlling objectives comes to two things:

1) Hold Objectives
2) Deny Objectives

Hold Objectives
You need troops to hold objectives. Once you hit 1500+ points, I suggest 3 troops just as a rule of thumb. The number you take ultimately depends on your army, as some troops selections are nastier/more resiliant than others. If you take too few, the other guy might decide to just KO your troops and make you fight for a draw. It's a very real risk, and it's happened to me.

You have two basic choices for holding objectives: You can take a dedicated squad to hold it, or you can just bring several mobile choices and make sure you have troops on the objective by the end. If it's a dedicated squad, ideally it's got a long-range weapon or two in it (IE: Space Marine Scouts w/ Sniper Rifles, Missile Launcher, Telion, camo cloaks).

Deny Objectives
There are two ways to do this: kill the troops on/near them, or contest the objectives. If you have stuff within 3" of the objective, then he doesn't control it. We'll cover the 'killing them' part later, but the short version is that corpses don't hold territory*. Contesting objectives usually involves swift, cheap units. Sometimes it's a Tau Piranha or Marine Land Speeder, but empty transports can do the trick as well. In a pinch, you can tank-shock people off objectives as well, unless they're in a transport.

2) Kill Armor
Vehicles (and monstrous creatures) are a fact of life in 40k. You need to be able to stop them, or they'll run roughshod over you (sometimes literally, see 'deny objectives'). In terms of killing vehicles, you're looking at two basic types: lighter, and heavier. Lighter vehicles are AV10-12; Heavy is 13-14. You need different kit to take them out. Note that vehicles may not always DIE when you damage them, but sometimes it's enough to shake/stun them or knock off the main gun.

Light Armor
Usually, weight of fire is enough to harm/kill lighter armor. Things like scatter lasers and autocannons are your weapons of choice against lighter armor; S7 lets you threaten AV12 and usually comes in decent numbers. Most S8 weapons don't have the weight of fire to do the trick.

Most light vehicles are faster, and most transports are lighter-weight vehicles. Additionally, some heavier-weight vehicles have weaker flank armor (IE: A Predator has AV13 in the front, but only AV11 on the side).

Heavy Armor
Sometimes, the autocannon just isn't gonna cut it against your target. Sometimes, you need melta weapons or rail guns. Why melta? If you can deliver it to 1/2 its range, you get 2d6 for damage penetration, and s8 + 2d6 averages to 15, which is a penetrating hit. AP1 is icing on the cake, since it's +1 to damage results, or a 50/50 shot of killing the vehicle on a penetrating hit.

Some armies have access to S10 shooting (Tyranids and Tau), and this has the raw strength to go through AV 13/14.

Taking it for the Team
Note that with melta weapons, you probably WON'T get a second shot, AND you are close to the enemy. It behoves you to have some cheap, sacrifical melta units just so you can take out higher-cost targets. Triple land raider sounds fun until someone trades 3 landspeeders or 3 squads of guardsmen for 750-800 points of your army.

Vehicles and Assault
Most vehicles have AV10 in the rear, so monstrous creatures, powerfists, dreadnoughts and the like can damage or kill them. Vehicles can counter this by moving and making it more difficult to hit, but lose the ability to use some of their guns.

On Monstrous Creatures
While there are some differences between vehicles and monstrous creautres, know that the same stuff that hurts vehicles usually wounds monstrous creatures. You generally want to throw AP2-3 fire into monstrous creatures just to deny them armor saves.

3) Killing Troops
Like vehicles, troops tend to come either in larger numbers of cheap, not-so-durable guys or fewer, tougher troops. Compare the Termagant, at 5 points, with an almight S3, T3, 1 wound and 6+ save to the Plague Marine, with T5, a 3+ armor save and Feel No Pain. Note also you can get 4 termagants for one plague marine...

Now, with infantry, you generally want to pile on the wounds. Weight of fire works on infantry in general, as you'll generally wound/kill the lighter troops and you'll force the heavier ones to take more saves (which they will eventually fail). Note also that infantry love cover and will generally have access to at least a 4+ save; marines and their ilk can operate in the open and fear far fewer weapons.

Weapons of note for anti-infantry work:
1) Flamers
2) Blast Weapons
3) Small Arms
4) Assault

Flamers
These are generally for killing lighter stuff; S4 AP5 or S5 AP4 combined with no cover saves is good for nuking as many orks/termagants/non-marines as you can fit under a template. It'll still force saves on marines and the like.

Blast Weapons
Blast weapons LOOK good on paper, but if the enemy uses their 2" coherency to the max and lines up properly (IE a line instead of a group hug) they can make sure you don't hit that many troops with a large blast. On the other hand, blast weapons in crowded areas are likely to hit at least SOMETHING, but this can include your troops if they're nearby.

Small Arms
Frankly, most infantry have these. It's not your ideal weapon, but if you catch the enemy out in the open or shoot enough of them with these, they'll work. Everyone laughs at lasguns until 30-40 guardsmen point them at you...And even a 10-man tactical squad can crank out a fairly respectable number of wounds.

Assault
Not everyone belongs in assault. Those that do tend to have either a LOT of attacks, or good quality of attacks (IE: ignore armor saves and decent strength) or both. The poster child for heavyweight assault troops is the Thunder Hammer/Stor Shield Terminator. While they only have 2 attacks each, they are hard to kill (T4, 2+ armor save, 3+ invulnerable save) and hit hard (S8, ignore armor saves, and survivors go at I1 next time). The flip side is something like the Hormagaunt, which is only 10 points for something with S3, poison, and 3 attacks on the charge with Furious Charge and I5 base.

In Summary
While this IS a critical-hit wall o' text, I (and others) could easily go into more detail on the various points. I think I've covered the salient, basic points for the scenarios you'll commonly see. I mean, most of the time you'll have to deal with objectives, and all armies can bring vehicles (or MCs) and infantry. I will probably try to break these points out in greater depth for my next few non-hobby articles.

In the mean time, I've got a heap of bugs to paint, and still have Tyranid Primes, Hive Tyrants, Hive Guard, and Harpies to convert. There's also 30,121.57 Termagants to paint. Finally, there are the Trygons to build...but it's all good.

*Unless it's zombies.

Evaluating Units Honestly: Opportunity Cost

Aside from being a stupidly catchy song and amusing video, the song emphasizes a point: "You can go with this, or you can go with that," (Or you can blow it up, but we're trying that too, aren't we?). Blame Haihastur too for this one, since he touched on it in the comments here.

Defining the Term
'Opportunity cost' is a $20 term you'll hear in economics class that explains the idea that 'there is no such thing as a free lunch.' So, let's say someone buys you lunch. You spend time, go with them, eat, and may or may not enjoy yourself, the food, the company, etc. Right? Perfectly plausible.

See, the thing is that the lunch never cost you MONEY, but you still had to spend the time. You could have eaten somewhere else with different company, or simply worked through lunch and gone home early that day (assuming your workplace would let you).

The fancier definition is that when you pick one option, the opportunity cost is what you give up from the second best option. IE: I have $1 and a vending machine. I can buy a Nutty Bar (mmm, peanut butter and chocolate...) or a Coke (mmm, cleans engine parts AND refreshes!). If I buy a Nutty Bar, the opportunity cost was the coke. If I buy a coke, the opportunity cost was the Nutty Bar. If I don't buy anything, the cost of $1 was not eating from the vending machine.

Make sense?

Opportunity Cost in 40k Terms
Let's walk away from the vending machines in the break room and look at the force organization chart. I'm allowed 2 HQ choices, 3 elites, 6 troops, 3 fast attack, and 3 heavy support. I'm also allotted a certain amount of points per game, and I'll generally have to field one HQ and two troops selections.

We'll have to compare Opportunity Cost two main ways in 40k: force org slots and points.

Force Org Slots
Here, we're comparing options within a given force organization slot. Well, we have to have an HQ, and we have to have two troops (and will often go for at least a third, depending on the army). These are non-negotiable slots, so what we put in them is part of the army's 'theme' (in that you want something like light or heavy mech, or foot, or massed MCs, or horde, or whatnot).

Similar Roles
Here, we're talking support. It's simple, because we can limit our comparison to the slot. This is where Haihastur started this. If I recall correctly, he's not a fan of Vindicators in the Marine codex (and frankly, I'm not either), but prefers Whirlwinds to Predators.

Well, we have 3 heavy support slots, and we probably want to at least duplicate the choice for sake of reliability/resiliency (aka, redundancy). So, we're comparing the capabilities of two potentially disparate units. We should ask ourselves:
1) What capabilities does it bring/what does it kill?
2) What does this do for the rest of my army, potentially?
3) What's the point cost?

The Heavy Bolter/Autocannon Predator is more or less the same price as the Whirlwind, so price isn't an option. We then need to ask what do they do, and what do they bring for the army. This is a nutshell example, so I'm not going to give you all a full Vindicator vs Predator comparison. Short version:

Predator
-Worry light armor w/ heavy bolters, autocannon
-worry medium armor w/ autocannon
-durable AV13-front vehicle; one more target to deal with
-worry monstrous creatures & infantry, but loses effectiveness to cover

Whirlwind
-maim up infantry w/ S4, AP5 ignores-cover shot
-prefers to hide
-single weapon system = one damage result to gimp it.

My opinion leans towards the predator because it can do more than the Whirlwind (engage vehicles/MCs/infantry), even though the Whirly can scare lighter infantry even if it's in cover (assuming they're AP5) and can still respectably wound heavier infantry with the S5 shot.

Disparate Roles
So, let's look at Fast Attack for Space Wolves. They can bring the respectable space marine land speeder, but also have Thunderwolf Cavalry. Both need to be brought in numbers, so they generally preclude the other. Here, we're talking about something that potentially flavors the army; bringing 10-15 thunderwolvs is a hefty points investment and makes them the centerpiece of the army (and they can be a bloody scary one at that).

A tyranid example would be 2-3 Tyrannofexes versus 3 trygons. Taking Tyrannofexes means you've got a ranged shooty core to the army, whereas 3 Trygons means you're going to be in the enemy's face and that'll dictate how you build the army.

The same can easily be said for any Space Marine commander with Chapter Tactics in lieu of combat tactics, or any strong supporting HQ figure (IE: Farseers for psychic support/defense, Hive Tyrants for reserves manipulation/preferred enemy, etc.)

Comparing Capabilities
The other basic form of opportunity cost comes in the form of similar capabilities in different slots. This is something you'll find more of in newer codices, as this allows you much greater flexibility in terms of making an army, but complicates army building a bit since you're weighing more options. (I'll take the extra work, personally).

Let's look at the IG book. I don't know about you guys, but I like poofing infantry in great bloody swathes. Do you like that? I also like chunky spaghetti sauce, but that's unrelated.

So, if I want to KO swathes of infantry, I have several choices, including:
1) Hellhounds in Fast Attack
2) Valkyries with Missile Pods in Fast Attack
3) Multiple Chimeras w/ Hull Heavy Flamers in troops, other slots
-possibly Platoon Commands in aforementioned chimeras with flamers, too
4) Leman Russ Eradicator in Heavy Support
5) Colossus Siege Mortar in Heavy Support

All of these are capable of doing horrifically graphic things to infantry, though not all capabilities are necessarily equal.

My evaluation will also depend on what other essentially capabilities I can get in other slots, so I'm still doing some intra-slot comparison. I could take Hellhounds (which can get hull multi-meltas for some duality), which means I need to get some more reliable anti-tank elsewhere (Maybe troops or heavy support, but not Vendettas. Maybe Hydra flak tanks and meltagun squads?). Or, maybe I take the Russ Eradicators, filling up my heavy support and leaving me with the need to bring anti-tank in other slots (Maybe vendettas or melta squads?).

Wrapup: Opportunity Cost and Army Design
Basically, you need to start by knowing what your army can give you in what slots. Some armies make this simpler than others. With Eldar, I know I want to bring Fire Dragons to kill heavy tanks, because they're a solid option (...and I don't really have other good options for killing tanks). I can supplement it with S8 guns from transports and falcons, but I just don't have any other comparable punch, so the rest of my army can fall in after these choices are locked in.

On the other hand, better-designed armies can bring the capabilities in various slots. Here's where you have to do the work and take the concept of opportunity cost into account: you want redundancy so SOME of your tools live to do the jobs, so you're going to generally make one choice for the non-troops slots and duplicate it. That's why you need to get a grasp of tradeoffs.

Hopefully, this has been beneficial (or at least thought-provoking), but it seems like tradeoffs are A) a complicated part of army-building at times, and B) sometimes overlooked.