I switched from Avis to Hertz and haven't looked back. Most of the airports I fly to I can pretty much pick any car in the lot (Pres Circle, 5 star, or Gold), and our corporate rates are almost identical to Avis. For weekend rentals I book through United, and typically find competitive rates. If the rates are high on United.com, I book our corporate leisure rate and pass on the UA miles.

For quantification, I have rented 18 cars for personal use this year for a total cost of ~$1,100 (including taxes and fees) and have received 75,250 United miles for those rentals and 550 Hertz points (for the bonus every 15 rentals)