Wraithlords are the Eldar equivalent of a Dreadnought, a massive (well, they used to be) wraithbone chassis piloted by the soul of a dead hero. The Wraithlord is quite hard to kill, with 3 T8 wounds and a 3+ armor save, and he packs a fair punch with 3 S8 attacks as a monstrous creature. He can carry two heavy weapons so he’s a decent fire support unit, and he can carry a ghostglaive, which is master-crafted and gives him +1S. He also comes with two shuriken catapults, which you can (and should) exchange for flamers.
The Wraithlord is a very useful generalist unit. He can carry two heavy weapons, meaning that he adds to your army’s firepower, and he’s a threatening assault unit, so he makes a good counter-attack unit to support your firebase. His one real downfall is his slow speed, so don’t expect him to advance on the enemy and make it into combat early enough to be useful. It’s also important to note that Wraithlords are characters, and can tie up even very nasty assault units by challenging out their characters. I’ve been on the other side of this and it’s tremendously frustrating.
I generally run Wraithlords with two heavy weapons, either paired bright lances or scatter lasers, and two flamers. That way, he can take out enemy armor or infantry and he can torch enemy light infantry that get too close. I would take the ghostglaive as it’s quite cheap for what it does, but I only have the old metal Wraithlords and I can’t figure out how to put a sword on them that won’t look stupid.
The Wraithknight is the Wraithlord’s bigger, faster cousin. He’s just as tough and has twice as many wounds, though he only has one more attack. He’s a jump monstrous creature, so he’s much faster than the Wraithlord. Base, he comes armed with two heavy wraithcannons, S10 AP2 Distort weapons with decent range. These are great for taking down vehicles as well as monstrous creatures due to the chance to cause Instant Death.
The Wraithknight can switch his wraithcannons for a ghostglaive and scattershield, but this really doesn’t make him any better in combat. You get a master-crafted re-roll for the loss of your excellent cannons, and you have to pay points for the privilege. If you want the shimmershield to make the Wraithknight even tougher, take it paired with the suncannon, a starcannon that fires three blasts. It’s expensive, but at least it’s a useful weapon.
The Wraithknight can also take some expensive shoulder mounted weapons, but I would avoid those in most cases. As a monstrous creature, the Wraithknight can only fire 2 weapons, so taking additional weapons with the heavy wraithcannons is pointless, and you shouldn’t be taking the ghostglaive version anyway. If you take the suncannon, you might as well take a scatter laser to twin-link the suncannon.
The Wraithknight is a serious fire platform, able to engage heavy targets and mobile enough to get line of sight on difficult targets. It’s not a huge assault threat, but it’s more than capable of beating up units without high strength attacks. The wraithlord is most useful for its tremendous durability and speed. It will likely survive to the end of the game, at which point it’s speed and killing power will be very useful.
So which one to take?
A Wraithknight equates pretty well to two Wraithlords. They have the same number of wounds and cost similar points. A Wraithknight brings two heavy wraithcannons, but the Wraithlords can have four bright lances that can engage two targets, so I think that’s pretty even. The Wraithlords have the advantage in close combat with more attacks and cheaper access to a ghostglaive, but the Wraithknight has the advantage of being faster.
In general, I think the Wraithknight is the better choice as it only takes up a single Heavy Support slot, allowing you to pack in more Wraithknights or just leave more room for heavy firepower. It’s mobility is also a major factor, as it will always be able to get where it needs to while the Wraithlord will often spend turns out of position. Even so, the Wraithlord is a fine choice if you’re short on points for a Wraithknight or if you’re not planning to fill all of your Heavy Support slots.