People keep comparing damage output of team vs. team, when I can't see how that matters.
Because there are absolutely no non-renewable resources in battle, shouldn't the focus be on sustainability? That is, you maximize healing and defense so that you can stay alive indefinitely against the most difficult opponent you can. How quickly, then, you can kill that enemy is irrelevant. Shulk + Reyn + Sharla might be the most sustainable combo...it might be slow, but the big uniques have so much HP that you need to be able to survive for long periods of time no matter how quickly you can deal damage.
Edit: Spoiler above has no context and should be immediately edited.