There are many car rental companies in the US. A friend recommended AVIS, so I didn't spend much time comparing. Based on what I saw, AVIS seems reasonably priced among the bigger companies. Companies like HERTZ are quite expensive! AVIS and BUDGET are part of the same company, and I guess AVIS might be slightly more expensive. They have a lot of new cars (as big companies typically do) and great service. They don't push for extra insurance and are very considerate. We arrived at Bozeman late, around 1 AM. The staff was patient and explained that while they could give us the car early, there would be an extra charge unless we returned it early. Extra drivers cost about $15 per day, which is cheap. In San Francisco, AVIS does not charge for an extra driver.