I have been unconditionally loyal to Avis for years and they have treated me exceptionally well. But they are also expensive, I think, and I'm trying for alternatives.

I have had a bad experience with Alamo, but whenever I've had a problem with Avis they've always fixed it. OTOH, I rented a car in Houston for 1 day and 2 hours, a low end car, they upgraded me to a Nissan Altima and it costs $128