Ive just aquired both and have had a closer look at them.
The P/S Cursed Birman
looks fairly underwhelming at first glance. But it has one obvious combo in Prowl + Call Darkness. But that effectively wastes your points in speed, dropping you from 289 speed to 202 speed.
The other combo is Spirit Spikes+Devour, giving you a bit more of a tanky setup.
The slot 1 abilities seems fairly bad as well. Not being a really speedy pet, its not guaranteed to get decent use out of Pounce. And Spiritclaws, while much nicer damage, requires moonlight for optimal use. Something which Birman cant provide himself, unlike Xu-Fu.
Only saving grace is the Undead racial, imho. Even if its weaker the faster you are.
The other pet Widget the Departed
has a much better designed skillset, even if it also have spirit claws. Being S/S it can much more reliably make use of Pounce, and it comes with a better combo in Call Darkness and Spectral Strike.
Sure it could use Prowl+Spectral Strike, but would need a feeder pet for Call Darkness or Blind, besides neutering its 325 speed. Pounce, Spectral Strike and Call Darkness looks like the optimal setup for this pet, imho.
Widget the Departed is the clear winner of the two new spectral cat pets imo. But both pets should have had Sneak Attack
instead of Spirit Claws, wouldve fit them -MUCH- better!