I could have massed more marines...But switching from a banshee rush start to teching to thors, and getting them out would have taken way too damn long. Even if i got them out to my expansions they probably would have gotten zerging owned. Vikings do more damage than mutas and cost less don't they? And they can shut down muta map control without worrying about zergings or roaches, which my oppenent had plenty of, and I could have handily eliminated with banshees once I had air dominance.
So basically my opponent had roaches, zerglings, and a lot of mutas, with which he was doing a lot of map control, shutting down my attempts to expand. My strat was to gain air superiority with vikings and then clean out the zerglings and roaches with banshees.
From what I can see my main fault was trying to stick to early banshees, which prevented me from massing enough vikings to counter the mutas.