Have used
Alamo/National. Like other they poster they are the same company, Alamo is usually less expensive. We like National best because using EA you can get your luggage, walk out to the garage and just pick out whichever car that's available in your class. Drive to booth, hand person DL and away you go. Alamo works the same way after you use the kiosk which takes about 5 min. You actually select your car from National.
Got a great deal through
Avis for both our upcoming Oct & Dec. trips. DH is preferred member so we can just go out to the garage there, but Avis picks out your car for you. They usually give you options.
Dollar is okay used them once. No line at the counter. Thrifty is about same except Blue Chip you can go to garage, they also pick out car for you. Right now they have some good prices using the Orlando Magic card.
Carrentalsavers.com is a good site to price and mousesavers.com has lots of codes & coupons. I would use rental company that is in the terminal, which all the above are. The shuttle to your car can take a lot of time for both pickup and return.