Kezzik wrote:resto druids literally only use 1 spell: healing touch
Probably troll, but that's really inaccurate.
Anyway, priests are the "best" for straight up raw healing. Druids are interesting... some fights they are really strong; mostly fights where you can roll rejuv on the raid (mag, firemaw, decent on vael). Their big problem is that healing touch is really bad, but necessary to use a lot. Pallies are kinda like priests but more mana efficient. They can flash of light for a long long time and not OOM, even without mana pots. IF you want to show up to raids with no consumables, pally is your class. I'm partly joking on that point, but I think it's basically true. They still play an important role of course.
It would probably be hard to know what you'd like before you try it; safest bet is priest though. Druid is probably the most challenging, because you don't have anything like flash heal / flash of light. I've played a ton of vanilla priest, but if I had to play something else, i'd be druid for sure.
I don't typically play horde so I won't comment on shaman.