Human and Draenei are a good toss up since they each offer benefits. However due to Blizzard not having a clue, Human is better.
Draenei
Gift of the Naaru: Heals for almost nothing worth noting.
Gemcutting: Jewelcrafting +5. Woo. Worthless. Until Blizz gets it in their head to make Draenei ONLY cuts(455 now, 530 in Cata) this is junk.
Shadow Resistance: 2% Shadow dodge. Woopdidoo.
The ONLY good, Heroic Presence: 1% hit for everyone in party(not raid). This effectively shaves off a bunch of hit rating. As Arcane, you already get 6% Hit, so now you only need 11% total. Crazy easy.
Human
Perception: Stealth detection+5. Meh, decent for PvP I guess.
Sword/Mace Specialization: Worthless as Mage.
Diplomacy: 10% Rep gains. Amazing for grinding rep.
Every Man For Himself: PvP trinket for free. Instantly gets you out of stuns/binds. Super useful, especially in PvP.
Human Spirit: 3% Spirit boost, great for free crit.
Human overall wins by a landslide, but Draenei not only look WAY cooler, sound WAY cooler, and overall are more awesome... they get the 1% hit.
Aside that, Human wins.