Haven't used either but we always use Priceline, which winds up being on par with those. They only use National, Alamo, Hertz, Avis and Enterprise, all of which are located in the terminal. We wait until we are about 10 days out and can typically expect to pay around $12 a day for a Standard/Full Size.
We've never had any trouble using our AAA discount with Hertz or Budget. We are using Hertz in February to rent a car from Universal to Kennedy Space Center. We are planning to use the Universal Shuttles to get to SeaWorld.