i think wraithlord because it can survive longer, and get of more shots that have a chance of doing somthing

 

lets be fair, you will rarely be out of range with any of the three, the thing the other two give you the WL does not is manouverability, it is far easier to hide from a WL than either a falcon or a serpent.

BUT that right there is breaking the cardinal rule of eldar, dont just consider things in isolation

I have 2 main long range anti tank options in my army and Ican take one or the other, one is the nightwing, the other is a war walker with 2xBL, in either case it is there for AV14 things, I have plenty of str6 shots and singing spears about, so whilst the first bit, either the NW or the walker, is weak, by the time you have considered the rest of the army it is fine

 

I don't play eldar, but I do play tau, so my advice might be a bit off here, but I wanted to voice my opinion.

I think, much as cher has said, that you have too look at the whole Heavy Support slot. Personally, the falcon doesn't scare me that much, nor does the fire prism after the first turn or so. Sure it's fast, but a single glance (which isn't too hard considering the AV) can effectively prevent it from firing, and therefore cuts it's effective shots in half. I have this same problem with the Hammerheads I run.

I've began running a broader list because of it, and I think the eldar could benefit from the logic as well. A single wraithlord might not be deadly (but the model is so cool), but couple it with a pair of falcons (or fire prisms, to taste) and now you give your opponent and interesting problem. To kill the wraithlord with anti-vehicle weapons means that you can't shoot the falcons, and to ignore the WL for the falcons means you're going to get pummeled because you simply can't stop the WL from moving and shooting.

This comes from my experience of having 3 HHs getting glanced every turn. A pair of Broadsides (equal to a Wraithlord) and a pair of Hammerheads is a more effective anti-tank, and I would bet that a wraithlord and 2 falcons (or 2 WL & 1 Falcon or fireprism, as you prefer) might provide a more effective anti-tank solution than 3 of any one thing.

Just my two cents, I hope my tau logic made a little bit of sense.

 

Especially with the eldar, "best" is sort of a tricky question. The eldar are more than any other army a conglomeration of specialists that work in concert to acheive victory.

It really depends on how your army functions to really flush out what "best" is.
For example, if you play a guardian heavy army with lots of support weapons and good dakka. Then WLs or support weapons may be the best option for you, even war walkers.

If you play a fast zippy army with lots of mobile parts, maybe falcons, or a fire prism may be the best for you.

What supports your army best to fulfill a specific role is more about how the rest of your army is planned, though it could very feasably be planned AROUND your primary anti tank weapon of choice.

 

according to actual stats (where as the real answer is mentioned above about what army your really using) i would say WL are the best, they are resilient, have a good BS and can adapt to different threats. thier 1 drawback is thier speed, but with the range and some support that can be overcome.

the falcon is very resilient, however it is more of a sub-AT unit, sure they can kill tanks, but when 14 armor is sitting in front of you, just hope you might be able to get a decent side shot to have a decent chance, with the low BS you really have to trust luck.

the prism isnt as resilient, but what it lacks in surviveability it makes up in punch. it has long range, a good BS and a very versatile weapon. this is a literal terror for most armies.

the key note is as above, which is going to compliment your army best, if you have a speedy army, your just going to leave the WL behind un-aided. where as if you have a foot slog army, your skimmer AT might not have the manueverability with all the troops congesting into a small area.

in pure stats, WL

 

Well it depends on the size and type of armour you are facing. A 14 armour land raider is best taken out by a brightlance toating wraithlord (or maybe a brightlance waveserpent). On the other hand a 14 armour monolith requires the subtle touch of two fire prisms. On transports a falcon excels.

 

On the other hand a 14 armour monolith requires the subtle touch of two fire prisms. On transports a falcon excels.

hehe, subtle like a sledgehammer! this statement cracked me up. ;P