Avis Preferred is usually better/faster than Budget FastBreak. Even with FastBreak you often have to stand on line to see an agent, although it is a dedicated line and they typically have your paperwork pre-processed as a FB member, so it theoretically should be quick, but Avis Preferred is still more seamless since you can skip the counter entirely.

As far as vehicle selection, it can be hit or miss. By and large, Avis should have the better vehicles, but it often depends on timing and luck. Regardless, we'd probably recommend Avis over Budget for a small price difference.