If you do a search on Travelocity it will tell you which companies have on airport facilities either with or without a shuttle and which don't. Of the ones that are in the terminal I have found that Dollar tends to have the best prices and usually they will let you choose which rental car you want (from the class) as opposed to assigning you one. I like that because as a car buff I can usually tell which are newer models (or I will look at the registration to see what model year it is). I also like that Dollar's "midsize" cars are actually midsize cars versus other companies where they offer cars that not long ago would have been considered "compact." Just remember if you book through Dollar's site to click the tab in the middle of the price list for city specials as that cuts the prices down a bit