You will most likely be locked to Resto at 60 unless you rly like feral and want to push the limits, but from what you said it seems that feral is not for you. Balance is kinda meh. And levelling is best as Feral, yes.
Regarding farming potential, it depends on what you want to farm. I think you have more options as Druid but on the other hand Priest has decent aoe farming potential opposed to druid.
Regarding healing in raids, Priest is overall better healer as they have multiple choice of heals so they can adapt to any situation. They are better at emergency healing with Flash Heals and shields. They have a little stronger healing over time spell and better aoe heal. Druid heals are less effective due to their longer casting time but can still do a lot of healing. Druid also lacks a normal ressurection which other healers have. They do have combat res though, which is always nice but on 30 min. cd. They bring other buffs as well as Innervate which you usually use on your Priests to boost their mana regen. Druid also has better mana efficiency then Priest.
Faendur, the Creepy Dwarf