Want to make a healer...
Would say priest's main advantage is having 2 healing specs.
But any healer will do fine, there are some that are considered weak atm but with 5.2 coming out it can easily switch around who is the strongest and weakest.
If anything, I would recommend picking a healer that you enjoy the off-spec you choose as well.
I had the most fun though leveling my Holy Pally in BGs. I was almost invincible and probably really pissed off a lot of Horde when they couldn't take me down even when it was 6 vs 1.
And enjoy the switch. I'm healing this xpac after six years of only tanking in raids (well, I'd heal farm/alt runs during Wrath, but that doesn't count), and I'm loving the change of pace.
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