Like airlines I suppose. We are top tier Hertz so usually get whatever car we would like. Without status I'd probably go for Enterprise (who let you pick form cars in whatever class) or pay extra for Hertz which I believe has a fee you can pay to pick your car.

In my experience Avis is one of the worst over the past couple of years. Dollar is OK unless it's a big holiday or otherwise busy.

SFO has a plan where if you rent a hybrid you get $15 off. We got the Altima Hybrid which was SWEET! from Hertz...

http://www.flysfo.com/web/page/tofro.../greenrentals/




(We're in SFO but rent cars pretty often. )