Can't speak for the others because I've always gotten my best deals with National - and they couldn't be any more convenient than at Orlando. Just take the elevator down to the bottom floor - check in at the desk - exit the doorway behind the check in counter and you are in the underground garage where the cars are - pick up your car and drive out of the airport. Return is even easier - just reenter the airport into the bottom floor garage - check your car in with the attendant waiting in line- walk across to the door - and take the elevator up to check in - wish all airports were this easy!