WoW pvp classes, which is better?

I have a Ret pally, frost DK, and a mage and was wondering which one I should level. they are all around lvl 60 and hearing how badly Ret pally's are now I'm not sure If i want to play it endgame. I'm looking for more of a pvp type class but will pve as well. What are you're opinions on each of these classes?