Eladrin who start with 13 DEX post-racial can qualify for Wizard Implement Mastery, and thanks to the wording of Eladrin Sword Wizardy, they can get a 19-20 threat range while still using a Cunning Weapon. This is cool if you've got a Violet Solitare, because it means more action points. They can also pick up Arcane Reach at Epic, which is useful to have for Thunderwave and Prismatic Spray. You'd probably also fit in Dual Implement Spellcasting in this case. The ability to train Perception out the gate is a small perk but one I think worth mentioning. Granted, most of these are just damage boosters, but if Blood Mage is your paragon path of choice, you might care about it.
The Deva, on the other hand, can pack in obscene accuracy. Gunning for 20 INT with Memory of a Thousand Lifetimes and Terrifying Insight means the control will hit where it needs to: who cares if you're dazed all the time if there's no one around to actually hit you. The ally buffs are cool, and then you can force a crit on your stunned opposition to get an action point with the Violet Solitare that you'll use to recharge your dailies. The skill bonuses and defensive perks are just gravy, Nercotic resistance can be very powerful.
Humans are probably the strongest out the gate, but I think by mid-paragon their benefits start to matter less and less. Who cares about a 3rd at will when all you need are Illusory Ambush and Thunderwave? The free feat gets spent on Action Surge - Devas and Eladrin don't have tempting racial feats for an orbizard anyways. By Epic when you have Spell Mastery, you might be more interested in using action points to nab back daily power, too.
I'm not entirely sure what's best: Eldarin Blood Mages look like a lot of fun since you can tack on a striker-secondary feel, but a Deva Divine Oracle really takes control to the extreme with a hint of leader, wheras I see Humans offering a little more flexibility at Heroic.