Tauren or Night elf, it depends on your talents, and how you go in the different talent trees.

Feral
cat/melee dps: Night elf (dodge)

Bear/armor tank: Tauren (HP and armor)

Balance
Night elf (you can use shadowmeld in moonknin form and you have more intellegence)

Restoration
I would choose Night elf because of shadowmeld-usable in tree form and Night elves have more intellegence but Taurens DO have more HP and Armor to last longer.

+a bonus, The Night elf druid's and rogue's shadowmeld is harder to see than other Night elves'. PEOPLE UDERESTIMATE SHADOWMELD, (huge bonus w/hunters lol)