I'd really just go for what faction you prefer. Personally, I like Alliance - though everyone says it's got alot of idiots in, which it does, the Horde is actually no better. Based on racials alone, Tauren have a useful extra Stamina, though this is only handy if you're a tank or PvPer. As a PvE Moonkin, I don't get attacked alot and don't minding having a little less HP.
Go for whichever forms satisfy you the most. Personally, I don't like the Tauren forms as much as the Night Elf forms. The Tauren cat form is kind of ugly, and a bird with horns just doesn't look right. To me, the Night Elf cat form is sleaker and prettier, and the ears on the bird form look very much like feathers, so they aren't noticable.
But, once again, based on racials, Tauren wins. An AoE stun can be very useful, even if it does have an irretating casting time. Once again, however, if you're PvE, you don't actually have much demand for it.