Airport Valet is also in the airport garages, the yellow shirt guys just past the other valets. I used them once via a LivingSocial deal they ran. I was generally satisfied, but can't really compare them as I haven't used the others.

I did find the ad-on services very convenient; I got the state inspection and oil changed, price comparable to the local quick lube place, with the work done while I was gone, that saved me a bunch of time. And I like that their daily prices drop for longer trips.

https://www.theairportvalet.com/prod...icingInfo.aspx