Well if having the mistwalker healing in the 3s means you being ret, I'd say go with the mistwalker. But then again, holy pallies got an annoyingly high amount of CC....So I guess it falls into the who plays better with their toon.
Paladin by a pretty large margin. Although they can get destroyed by casters pretty easily, the support they bring for melee is amazing. They may well be the strongest healer for physical-based comps. Double freedoms mean a lot with the cooldown on dispels.
Monks are kind of a joke healer for PvP, too. They've got strange throughput (channeling, orbs) and pretty much nothing to avoid CC aside from their high mobility. Their CC is actually not bad, but designed around sitting in melee range. Definitely bottom tier.
Paladin hands-down. They are amazingly fun to play right now. Clemency and Holy Prism are great, and I severely underrated Selfless Healer for too long.
MW Monks are good at surviving stuns, but that's their biggest niche. GC said in some interviews today that they're looking at MW and WW abilities to buff them in PvP. The representation is very low right now, even accounting for the leveling differences.