FRS does not require a license. With GMRS you are supposed to have a license - not that anyone does. Out of millions of handheld GMRS users I am probably one of a few hundred that actually paid $60 for a license.
Also, at one time, 8 channel FRS radios were less expensive than the FRS/GMRS. An 8 channel FRS can probably still be bought much cheaper. So if you want to spend a couple of dollars for a radio that your 4 year old can play with and destroy get an FRS. For any adult use, the 22 channel FRS/GMRS are so inexpensive that there is no reason to get anything less.
The extra GMRS channels give you a better chance to get away from interference - like the 4 year olds playing hide-and-seek with their $5 Donald Duck FRS radios.
FRS/GMRS radios operate aroung 400 MHz making them line-of-sight devices. The ranges given by the manufactureers are what you could expect given the most ideal conditions. Still, in the open desert they do pretty good and are great for communication between vehicles in a caravan or around a campsite in most all terrain. I prefer the higher powered GMRS radios, 2-3 watts, for whatever little range advantage the extra power can give me (even though increase in range is no more than the square root of the increase in power)