My decision is largely going to depend on what classes are still to be announced, I'm going to play whatever class seems the most interesting to me rather then make a choice based on a side.
Also, for the Good vs Evil people - this is just my personal speculation, but I see Bioware painting the Sith Empire side more as self centered neutrals rather then pure chaotic evil for the pure sake of being evil, especially the non-Sith classes like the Bounty Hunter. Not evil, just there to simply do a job, but isn't going to let morality or anything else get in the way.