You also have to bear in mind that Gnome gives no benefit to pve Shadow Priests, whereas a Draenei does.
I usually choose the race that I find the most aesthetically pleasing. Min/maxing is just nonsense, as it hinders your customization/enjoyment of your character. I'll probably get the standard response about how racials make a HUGE difference. They may save your ass on occasion, but a Worgen Priest can be just as good as a Human priest, and so on.
EDIT: Anyway, we can agree on the fact that the Gnome +5% mana and the Human +3% spirit are overrated, and that is really what matters.
Human or Gnome I'd say.
People should pick a race on looks, most racials are just a minor bonus.
Im Gnome because i like gnomes, not due to the mana. Sure as disc it helps having it and the PvP racial helps on some occasions.
(hagara for example in pve and pvp it helps as well) Therefor the gnomes racials aint only good cuz of the mana but the pvp racial it has will help as well.
While every man for himself does work on more effects (stuns), but its still only usefull on hagara hm perhaps gunship but none should be caught by shockwave.
Just to put that out there as everyone seems to only look at the +int.