As said, I want to know what the best Species would be for Sith Warrior, also I noticed in the Beta different NPCs react differently to you if you are one species or another, can anyone shed some light on if being a trueblood sith for example does anything for you in game(besides story)
During the storyline, you are treated as a pureblood Sith, regardless of your actual race. I would have to assume that would hold true for every NPC in the game (and it has for every NPC I've interacted with). I suppose it's possible that it doesn't. But it seems like that would be highlighted in the story more than it would from random NPC's or questgivers. Being a pureblood Sith absolutely has no mechanical advantage over other races.
In addition, I haven't participated in PvP yet. But from what I've read, the race choice makes no difference at all when it comes to PvP or PvE performance.