This is what I've been able to figure out...
FRS:
Pros - Cheap, simple to use.
Cons - Limited power and range. Think 1 KM or so, and substantially degraded without line of sight.
GMRS:
Pros - Fairly simple. Most have some sort of digital channels for a minor degree of privacy. More power than FRS which means slightly more range, perhaps out to 5KM, again with line of sight. Allowed to use repeaters to extend range.
Cons - Technically requires FCC license.
CB:
Pros - No license. Longer wavelength/lower frequency means that the signal propagates around barriers more effectively. Inexpensive and commonly used.
Cons - Commonly used = more traffic/junk on the airwaves. Longer wavelength means that efficient antennas are longer.
VHF Marine:
Pros - Can talk to boats and many airplanes. Propagates pretty well.
Cons - Not legal except for approved maritime use. Handy if you live on the coast though.
SPOT GPS SATCOM Beacon:
Pros - Alerts emergency services to your location via satellite anywhere in the world.
Cons - Doesn't allow communication, requires official infrastructure to be operational. Good for hunters and outdoorsmen though.
MURS:
Don't know as much about this but some people choose it.
HAM is going to give you the best range and options but requires more gear and a license.