In a PvE environment, I've had success with Priest, Druid and Shaman heals.
Pally has rocked in PvP, but aside from Holy Radiance, their AoE heals are a bit lacking.

Wild Growth for a Druid is as good as Chain Heal for a Shaman.
I do like that the Shammy has Earth Shield, which combined with Riptide is generally enough healing for most pulls.

Between the two, it is preference really.
I'd probably dual-spec them both, Balance/Resto and Elemental/Resto (as Mikekim suggests), then you can mix and match.
Or run dual DPS, for quests and trivial content, or dual Heals for very challenging content.