The biggest difference among rental firms concerns how rapidly you can rent and return a car. In most cases, the rest of your rental will be fairly similar no matter which firm you use, since all the major rental agencies use new cars and remove them from service after about 20,000 miles.

Agencies speed the rental process in three ways. First, rental lots can be located close to airline terminals, resulting in a shorter bus ride. Major firms such as Hertz and Avis often feature on-airport lots, while other agencies such as Thrifty typically use off-airport rental centers.

Some car rental agencies also offer express pickup services to shorten rental time. This allows you to avoid the line at the rental counter, which can be very busy when many planes have recently arrived. Hertz, Avis, National, and Budget even have programs that allow customers to proceed directly to a car and drive away without waiting in any line.

A third feature that can save time is a quick return service. These allow you to return a car without waiting in line. Some firms offer automated terminals, while others staff the return lots with parking lot attendants that can record return information on a wireless computer.

Altogether, services such as these will help you save about ten minutes on each end of a trip. However, this time savings does come at a premium. Renters typically pay an additional $10-$20 per day when choosing a firm that offers these services. As a result, you may want to limit your use of the fastest vendors to times when you require the extra level of service.