Luminara Unduli or Barriss Offee as my Jedi healer?

I have Aayla 7* but not promoted, waiting on credits, she's one of my favorite Jedi. Jedi assist with +50% damage is pretty sweet, stun on critical, as well as her counter chance.

As for the original Q, if it's for arena, Luminara because she hits harder. But in general remove your healers from arena and just hit for max damage/debuffs/stuns.