They are a different frequency bands. CB's are on the 27MHz range, and FRS/GMRS are in the 462 and 467MHz range. The radio in Aaron's MINI is FRS/GMRS but is vehicle mount instead of a handheld radio.
Personally - I have both Cobra and Motorola (actually made by Giant) GMRS radios. When driving, I normally use the Moto with a boom headset, set to push-to-talk instead of VOX. This works best in the convertible with the top down - folks can hear me... but I don't have to worry about it transmitting everytime a loud noise happens (often, in my car) or when I'm talking to my co-pilot.
I also have a Cobra 40 channel CB installed in my car, which I only use to monitor Ch19 when I'm on the interstate to listen to the truckers talking about LEOs, traffic and detours.
We have a pair of FRS/GMRS radios (handheld) and one earpiece/mic that we got at Radio Shack for ~$30. We mainly use them on rallies but they come in handy on other trips and activities. Definitely worth the money.
