From MCO, I would be fine with any of the 10 companies that have their cars on site. My personal preference rankings amongst those 10 are: National, Hertz, Avis, Sixt, Enterprise, Alamo, Budget, Thrifty, Dollar, Payless.
IMO Avis is the worst. We cancelled a reservation but they charged us for the full cost (over 1K) and I had to fight it out through the CC company. They said we didn't return it...well we never picked it up! I won.
As others have mentioned, they are off site and ratings aren't so great. I would not rent from them, I'd rather pay a little more and get a car at the airport from a better know rental company. You are kind of at their mercy when you are off site.