I'd say defiler simply because of the noxious debuff would fit like a glove with the sk for more dps but honestly any would be good since SK has fairly decent survivability on its own
Either would work well, both are fantastic healers and both bring something to the table. The defiler is better if you want a little more survivability but the inquisitor will bring more buffs and dps to the duo.
I duo my fury with my hubby's sk and he loves it. I tried my inquis with him and he just liked my fury buffs and heals better for some reason lol
I 2 box either my Defiler or Templar with my SK - because both those healers are slower leveling. For buffs, I want a coercer or a bard. If I were doing content where I actually needed heals, I like a Fury.