If the cost isn't the primary factor I've been very happy with the aisles that National has. When I was there in October they had a half dozen minivans lined up for you to choose from. As long as the company is on site it should be fine.
I wouldn't have any issues using 9 out of the 10 companies that are on site at MCO. Hertz, Thrifty, Dollar, Budget, Avis, National, Enterprise, Alamo or Sixt. I've used all but Sixt over the last few years.