Outlaw:
It's about the same as the current combat rogue
It has Ambush, an ability similar to Sinister Strike, and an ability similar to Eviscerate. Also pistol shot is which is a 20 yd range shot that slows the enemy by 50%. Outlaw has no sap or poisons
EDIT: Outlaw still has the 50% bonus AP passive, so it will probably be viable for the 1 shot potential that the other 2 specs don't have
Subtlety:
Subtlety doesn't have ambush, but it has sap and backstab. It really doesn't seem too viable in the current state, it has no good mobility or slows.
Assassination:
It seems like this is going to be the best spec by far
Assassination doesn't have ambush as well but it has sap. It is the only spec that can use poisons, in which it can use deadly poison and crippling poison at 19. It has a 40 yard range ability called throw poison which poisons an enemy up to 40 yards away (essentially a long ranged slow ability). But most importantly it has Shadowstep, so not only does it have a lot of slows but also amazing mobility. As for damaging abilities it has mutilate and envenom.
All 3 specs have Evasion, Kick, and Crimson Vial (Instant 30% heal on 30 sec CD)
EDIT: Just noticed this thread is under the 20 twinking, assa rogues get a passive ability that refreshes slice and dice when you use envenom, but besides that everything is the same as 19
