Go through MRS several times a year and they're all much of a muchness. The offices for all the hire companies are small shacks, and there are none of the frills you might expect at larger airports (eg display boards for Preferred customers). The desks are not in the airport concourse, they're in little huts in the parking lot.

Avis used to be dreadfully slow and congested (queues out the door) after the BA flight came in, because that was the only rental company offering BA miles. They do now (at last!) have a Preferred counter, and twice in the last year I've had to claim compensation because I haven't been served quickly enough (your car in 3 minutes or £20/€30). Hertz are similar.

Note that through both Hertz and Avis I've had arguments about car damage, so make sure that you check the car REALLY THOROUGHLY, and make sure even the smallest dink is recorded before you leave the airport.

Have to say I love Provence, and MRS is a nice little airport, but car hire from there is one of my least attractive experiences...

[Oops, just checked date of OP. Guess my advice is out of date now - sorry. How did you get on?]