My experiences with Hertz have been mediocre at best, lawyer involved at worst.
Avis counters vary so much by location. I was in MKE a few weekends ago and they've closed the Preferred desk in the ramp, and the counter was swamped. Except preferred. Walked up and out before the lady who was helping was done with the person she was with (signing all the contracts.) Maybe 5 minutes. Reserved a "manager's choice" and got a 4 door Tacoma. I usually prefer an SUV, but it was better than the Accent I was expecting.
Hertz? They accused me of damaging a vehicle I had overnight. When their lawyer letters started, I just had mine reply. Never heard back after that. I'm 100% certain the previous renter damaged it. They're my last resort for a rental.