I've rented at the PHX Advantage a few times (and will be doing so again next week) and have never had any issues. Advantage is owned by Hertz and I used to work at the neighboring Enterprise and got to know the employees at Advantage. I'd never hesitate to rent at any of their locations. I can't speak to Fox though. This thread may interest you:
http://www.flyertalk.com/forum/other...advantage.html