If I was just asked to pick (which I won't, I'm sticking to Dwarf for awhile), I'd probably go with Blood Elves, simply because I like Horde better and they're, for fear of sounding stupid, cool.
But the Draeni (sp?) sound interesting because, if I've heard right, they give you the ability to play an Alliance-side Shaman. Ooooh.. I can just imagine it now.
But I guess it'll just come down to Horde vs Alliance, and Legolas vs. Davey Jones. Pick away.