Anyone have an opinion on the best craftworld for wraithlords, specifically ones that intend to get up close and personal (does anyone run them as stationary guns these days anyway?)? I am thinking either Ulthwe or Iyanden. Alaitoc might be nice for helping them get to melee, but is much less useful from then on. So eliminating that I am having trouble deciding whether it is better to shrug off more damage or fight at full strength for longer.
I think the Iyanden Craftworld Trait is really good for Wraithlords. Ulthwé is of course useful for anything, but basically Wraithlords lose 1/4 of their damage output in wounds 3-5, and 1/2 of it in wounds 1-2. With Iyanden, they don't lose anything until wounds 1-2, and at 2 wounds they're still better off than they'd be without the trait.
A single Lascannon shot can slow down your Wraithlord's move speed, ability to fight, etc. But with Iyanden, it will always take multiple heavy weapon shots to cripple your Wraithlord; the enemy might as well kill it, it's much harder to "mission kill" it.
I think if you are not running a bunch of them, Ulthwé is a generally strong trait. I have had some success with my own Ulthwé list, the extra durability really helps fragile Eldar infantry, but probably would help Wraithlords a good amount, effectively giving them like 1.5 more wounds. Not quite as good an increase in full strength operating range as Iyanden, but not nothing, either.