The damage isn't really comparable between Harmony and Cataclysm.
That said, Cataclysm is incredible for making sure things die fast and in bunches. It melts faces; at level 32 I can one-shot buzzards with phaselock, since the initial strike does about 50% and the elemental effects will do the rest. It's very, very good.
Harmony, though, is just nuts if you're playing with other people. The ability to res people from any range with phaselock is wickedly powerful and lets you handle some things that you just couldn't otherwise. The healing sure doesn't hurt, either, but it helps teammates more than I've seen it help myself when playing this way; I tend to go down pretty quickly if I keep getting hit once my shield is gone. There's only certain enemy types that give Maya any trouble as it is, and the extra healing doesn't generally help a great deal with them anyway in my experience.
Both trees are good. Motion is underrated as well, though; it seems to be ignored by a lot of people and has some great abilities in it. Still, solo if you're looking for "best" tree go Cataclysm and respec to Harmony if you're grouping and want a support role.
Nobody likes the motion tree? I was planning on making Harmony + Motion Maya
I have a Motion/Cataclysm build. I invested a little in Harmony so that I can heal myself with phaselock, but that's it. Helios is much better when you build up the motion tree, Not to mention increased gun damage and some useful kill skills.