After rolling as a few more classes:
It depends on what I'm playing. As a fairly new healer I almost always give it to the other healer because I feel bad for them having to pick up my slack. On the other hand, in a 4-man it depends on a lot of things. If the tank was excellent and pulled massive mobs and kept them off me as I spammed cure/physick whatever. If the DPS slept mobs or just killed them super fast.
Helpful people almost always come first. Humor is a + as well.
Lots of things to consider.