Generally so long as you stay with the major names they are all about the same and most of them are now owned by largest companies. I just try to avoid the off airport sites if possible as they are the ones who seem to push for the unneeded insurances, etc. We used Budget on our trip to Alaska last November and had no problems with them. Be sure to avoid prepaying (unless cancellable) if possible as we saved $200 by rebooking a week or so before our Reno trip two weeks ago by moving from Avis to Hertz.