Well, it's been a while since I've done some Eldar articles, though I've dug them out of the box. I'm not satisfied with my Tau's transportation situation (read: no foam) and I'm not willing to subject them to movement 'til I fix that, which ought to be soon. At any rate, I'm going to compare and contrast the Eldar foot troop options: Dire Avengers, Guardians, and Rangers. They all have their own distinct uses.
Note I'm leaving out Guardian jetbikes; for one: they're not foot troops, and two: I don't have a lot of experience with them. I'll go into more depth on them later, I'm certain.
Dire Avengers are aspect warriors that specialize in killing it with shuriken fire. They're basic WS/BS 4 guys with T3, I5, Ld9 and a 4+ save. Each come with an Avenger Shuriken Catapult, which is an S4, AP5, Assault 2 18" gun. The range alone should tell you that you want to mount up.
You may take 5-10 per unit, and may upgrade one to be an Exarch. To be honest, I usually skip the Exarch. He costs 12 points to upgrade (which really gets you a second attack, I6, 2 attacks, and a 3+ save) and then must pay for wargear and powers.
Double Shuriken Catapults (Assault 4 regular avenger shuricat) [+5]
Diresword and Pistol (Power weapon that if it wounds you, take a Ld check per wound; if you fail you die automatically regardless of wounds left) [+10]
Power Weapon and Shimmershield (everyone gets a 5+ save) [+15]
Defend (15 points for making the enemy at -1 attack when fighting you)
Bladestorm (everyone's gun gets another shot, but no firing next turn. You're reloading)
The wargear is neat...but unessential. No matter how much you want to be, you're not melee troops, so you'll have to pass up that Diresword with your piddly S3. Defend and a Shimmershield won't save you from losing CC, and possibly getting swept.
Bladestorm? Folks are on the fence about it. If you're going to use it, at least pay the 5 points to let your Exarch dual-wield catapults. Over time, per the same cost, you'll get more shots off just firing Avengers two turns.
10 Regular Avengers (20 shots a turn)
7 Avengers + Bladestorm Exarch w/ Dual Cats (14 BS4, 4 BS5 shots a turn, or 21 and 5 with a storm).
26 shots over two turns, or 40. You pick.
Of course, there's always the issue of getting those shots off. You may or may not get two turns to shoot.. Bladestorm simply lets you surge the unit, or fire, advance, bladestorm, assault and try to off the remnants. It's a timing thing; bladestorm is basically the ability for the unit to throw a haymaker (look up the old John Wayne western movies, and then realize that such a looping punch might hurt, but it leaves you way the hell open.) and I mean that in every sense of the word.
In smaller games, they may be able to work on foot. I'm talking like 1,000, maybe 1,500 point upgrades. Or, just spamming them on foot.
Defend + Power weapon/shimmershield + fortune might see them act as a passable tarpit, but it depends heavily on what you want them to tarpit. You're Ld9, so you need to not lose the assault by more than 1-2. I mention it as a 'fair enough' loadout for them. I think there are still things that'll cut through them, like most harder-core melee troops. Should a regular SM squad charge you, that's 12 attacks (Assuming sarge brought a pistol/CCW), down to 6 hits, 4 wounds, 2 without and 1 with fortune. That's somethign you can tie. However, if it's a nastier CC unit, or has power weapons, you might not hold. I feel it's honestly an iffier thing, but it's something to note. I'd expect to hold basic troopers, but not CC specialists.
The other option for Avengers is 5 of them as the 'DAVU' or Dire Avenger Vehicle Upgrade. I believe Dverning coined this term. You shove 5 of them into a Falcon with a holofield and a few guns on it. Not a very spectacular job, but a job nonetheless. Plus, they're likely to survive it.
I'd suggest either 5 at 60 for the DAVU, or 8-10 as a regular shooty unit. Note that if you're shooting 'em, you want to Doom your target. Definitely 10 if you're going to footslog it, and I'd probably take Bladestorm there just to get some extra oomph there.
Rangers are Eldar that decided they hate their day jobs, so they grabbed camo cloaks, longrifles, boots, and left. I suspect once I get my office job, I'll consider this. Rangers are your camping snipers. They have a sniper rifle, and some neat rules for cover. These include:
The Cool Bits
-To-hit rolls of '6' are AP1
-Stealth, so cover saves are at +1
-Move Through Cover
BS4 is the only stand-out, past that there's a 5+ save and Ld8. Not terrible for 19 points.
Really hard core rangers cost 5 points more (and you take the whole unit as Pathfinders), and get even more benefits. Of course, they've also flipped society the bird and are permanent exiles. Probably don't take their boots off inside.
-To-hit rolls of 5 or 6 are AP1
-Cover saves improved by +2
-Ignores difficult terrain rolls
Despite the cool bits, these guys are objective-sitters; no more and no less. I think the Pathfinder upgrade is neat, but the biggest benefit of the Pathfinder upgrade is the fact they take a 2+ cover save as a basic bit. I'd consider a unit of 7-8 Pathfinders (at 133-152) a decent objective-sitter. Let them snipe once or twice, and if they do something annoying the enemy might try to plaster them. Then, go to ground.
Now, the question is, is the Pathfinder upgrade worth it? 24 points for a 'finder vs. 19 for a regular ranger. 171 gets me 9 Rangers, and 168 gets me 7 Pathfinders. That's about as good as we'll get for equivalent values, so, basic shooting.
9 BS3 Ranger Shots = 6 ranger hits, 1 AP1.
4+ to wound, so we get 0.5 AP1 wounds, 0.5 rends, and 1.5 wounds for a total of:
1 wound that ignores armor, 1.5 that don't
7 BS3 Pathfinder Shots = 4.6 hits; 1.5 of which are AP1
0.75 AP1 wounds, 0.25 rends and 1.25 regular wounds
1 wound that ignores armor, 1.25 that don't.
At roughly equivalent costs, the damage is about equal. Additionally, the increased chance to ignore armor makes me happy, as it makes them more suited for killing monstrous creatures. Wraithlords don't like snipers in general, but Rangers might very well take one down in two rounds of shooting. You also can relocate more readily with the Pathfinders, so I think I'm going to have to reconsider. Additionally, you always have that 2+ cover save, so yeah.
If the enemy is not a CC-specialist, Dverning notes that you can use Rangers to infiltrate and potentially get a first-turn assault off. I think the trick's more psychological than effective, but it can still have an impact on folks. You'll just need to infiltrate out of LOS, and you'll need the Pathfinder upgrade to ignore terrain and make sure you can swing. I wouldn't expect it to work against anything more frightening than Tau or IG, but it's out there.
Don't forget to cry if flamers get nearby; then Rangers go away hardcore. Yeah, even regular flamers make these guys hate life. Then you're out a camping unit.
I think you can kind of justify taking the Pathfinder upgrade. Any way you cut it, the unit's a pretty nasty sniper unit, but I don't think I'd ever really take more than one selection. Dverning's done some math on the subject, and the points-per-kill is about the same. The real difference is the cover save, but you can just go to ground for the same thing. End of the day, you're not losing that much killing power, and you have more wounds.
Guardians come in two flavors: Regular, and Storm. They share the same statline; it's basically a Guard line aside from I4. (which is to say BS3, WS3, S3, T3, 1 attack, and a 5+ 'save'). Both come in sizes of 10-20 per unit at 8 points a head, so they're at least cheap at 80 points before options and/or a Warlock option. Note that if you bring a Warlock, you really have one of several options for them: Destructor (Yay FIRE! S5 AP4 template), Embolden (re-roll leadership), or maybe Enhance if you want to try to mix it up, to get yourself up to WS4, I5.
Note also that if you intend to run Wraithlords, you could get a Spiritseer-upgraded Warlock in a guardian unit.
You are required to put two together as weapon crew, and you can take any of the larger Eldar weapons. Even better, it's on a little hover-platform that lets you fire even the heavy weapons on the move. The downside? They're still BS3.
You could theoretically combine them with a fortune'd Avatar and spam heavy weapons, but...if someone gets into assault with you, or they kill the Avatar, your ld8 and meager statline won't save you. (Also, if someone assaults you, and your Avatar counterassaults, watch them hit your Guardians and inflict No Retreat! wounds on your Avatar. Bad Stuff.) You're also looking at 110 for a BS3 bright lance; not exactly the most efficient or effective source of lance fire. I would have to settle on the Scatter Laser, so then you don't have to Guide them to hit stuff. In a pinch, there's the cheaper, shorter-ranged Shuriken Cannon.
95 points gets you 10 Guardians with a Scatter Laser. Yay?
They all traded in their dinky 12", Assault 2 S4 AP5 guns for pistols with the same statline, and a CCW. Much scarier, really. However, you do get the option to take two special weapons, so that's either 12 points for two flamers or two BS3 meltaguns. That's at least palatable, but requires a transport.
Importantly, it's one of only four freaking sources of template weaponry in an Eldar army. (Your other sources are Warlocks with Destructor [usually located in a Seer Council], Fire Dragon Exarchs w/ heavy flamers, or Wraithlords with two flamers). Add doom and a Wave Serpent, and you've got a way to delete infantry.
92 points gets you 10 with a pair of regular S4, AP5 flamers.
145 gets you a Wave Serpent w/ TL Bright Lance, and underslung Shuriken Cannon
I would ponder skipping out on the Destructor-lock, as he's another 30ish points attached to a unit that is pretty much either going to live to board the transport, or be shot/assaulted down the next turn. On the other hand, the Warlock w/ Destructor adds a Heavy Flamer equivalent template, which is S5 AP4. Note that if it's not a space marine, a heavy flamer kills stuff on a 2+. You'll still lose the unit, but he'll increase the lethality. It's really a matter of whether or not you can find the points after the 92 for the flamer guys.
To be honest, I kind of like the Storm Guardians more. They're a distinct niche-filler in the Eldar army. Regular Guardians want to be neat little objective campers, but you'd need to take them in greater numbers. Alternatively, you'd want to bring as many squads as possible to get...as many scatter lasers as you can. At least it's hard to silence the heavy weapon? Investing 30 points in an Embolden Warlock gives them a re-roll on leadership, but still...there are better ways to get rate-of-fire in an Eldar army. (IE: Vypers, and they're faster).
Foot Troop Summary
All of your foot troops are basically kitted out to kill troops. Avengers can be had in the smallest squads, but also have the longest-range trooper gun. They're not flashy, but the're reasonably competent at what they do. They're a bit of a generalist choice, but require a transport to get into range. Ld9 is fairly helpful for not running, and if you can get a couple turns of shooting, well, so much the better.
Rangers are campers par excellence. They need less support than regular Guardians, and I feel there are better places to get your heavier weapons.
Storm Guardians fill a certain niche in the Eldar army: FLAMER TEMPLATES. Sorry, it needed emphasis. They're a suicide squad, but at 92 points plus transport? It's not a bad way to go, since they'll burn some stuff up. Also, it's cheap, because you know a bunch of T3, 5+ save guys sitting in the open in front of dead stuff are gonna die for their troubles. Ironically, they'll be deploying in the 'death by flamer' squad out the back of their required transport.
A Note On My Mech Bias With Eldar
I tend to view mechanization as an Eldar strength. In part, it's because it's an army of specialists: You can't even try to grenade down a tank with Dire Avengers, you really DO need Fire Dragons (or the not-so-impressive BS3 meltaguns of a Storm Guardian squad), or an Exarch's missile launcher from Dark Reapers.
So, we need specialists to do the job. If the specialist moves 6" and runs, well...it's not really that hard to figure out where they need to go, and block them. Flamers and meltaguns, and even the Avenger shuriken catapults, do not have the greatest of range, and you would need to move at least a foot to get to an enemy that didn't want to be near you. Additionally, without the protective warmth of an AV12 vehicle around an Eldar, it's a T3 model with a 4+ save, and the foot troops are generally not cheap enough to spam. I mean, the basic Eldar Guardian squad is 80 points plus heavy weapon; you're almost at 20 guardsman in 2 infantry squads by that point. Not really the most favorable comparison, and Guardians are ultimately fairly limited.
I think someone might be able to make an Eldar foot list work (especially if they use Scorpions or Warp Spiders in the front; use that 3+ armor save guy to screen the rest of the army for a 4+ cover save), but it will be anything but forgiving and easy to use. That's me, though. Plus, I'd rather just sit in my annoying-as-hell-to-kill transports until needed, but that's me.