Out of the three, i'm partial to Advantage since they share the Hertz fleet. They have an online checkin service and I think (but not 100% sure) kiosks too.
Dollar and Thrifty are identical - if you're going to use them, sign up for their fast rental programs so you can use the shorter line.
I use Thrifty and participate in their (free) Blue Chip program. So there are never any lines. I just pick up my car in the parking garage across from the main terminal building.