If those are the only choices you are going to have, definitely go Tauren.
I am an alliance man, though i do have a few hordies, and out of dwarf and tauren you'll get better usage from the Taurens racials.
With dwarf you only have Stoneform to help you, which can be useful if you're poisoned during a fight as it's one of the very few ways to get rid of it.
As tauren you got the +5% health, and War Stomp, which can kick *** if ur taking on 3-4 mobs.
That plus i think tauren start off with a higher Str value.