Most of the priest racials are now available to all of the priests.
The non-priest racials of the race still vary, but things like Devouring Plague, Fear Ward and Symbol of Hope are available to all of the priests irregardless of race.

Shadowmeld will be of most help in world/battleground pvp. You are immobile in arena so its not the best there. Doesn't hurt to have.
I really like that humans have the pvp trinket as their racial now, and effectively perception always on. You basically get to equip/use two trinkets instead of one plus the pvp trinket.
Dwarf stoneform ends bleed effects.
Not sure if gnomes can be priests but the escape skill is very good in pvp.
Draenei get you the HoT, but with a cast time.. and priests already have renew which is strong; not my top choice for a priest race.

One of my teams is 4x Disc priests. A pain to level, compared to higher dps toons, but I think they'll be fun in battlegrounds (I'm on a carebear server).
I went human as my race.