Here is an expanded comparison I wrote up a while back that compares and contrasts various Jeep-to-Jeep communication options:
CB (Citizen's Band) benefits:
1) very inexpensive; new radio/antenna/cable/mount setup can be had for ~ $75
2) no license required, so everybody can use one
3) due to #1 and #2, CB radios are very common among Jeepers
CB downsides:
1) because everyone can use one, there are thousands of a**holes out there actively trying to ruin your experience
2) 4 watt maximum output limits legal users, keeping range very short
3) CB uses scratchy, static-filled AM operation
FRS (Family Radio Service) benefits:
1) uses handheld radios which are tiny, cheap, and widely available
2) no license required, so everybody can use one
3) FM operation for clearer sound and little interference
FRS drawbacks:
1) limited to .5 watt output, which keeps range extremely short
2) handheld radios must have fixed antennas, also keeping range extremely short
3) only 14 channels available
MURS (Multi-Use Radio Service) benefits:
1) no license required, so everybody can use one
2) FM operation for clearer sound and little interference
3) 2 watt maximum output provides slightly further range than FRS
MURS drawbacks:
1) even though external antennas are allowed, range is still very short
2) repeaters are not allowed, also keeping range very short
3) only 5 channels available
GMRS (General Mobile Radio Service) benefits:
1) FM operation for clearer sound and little interference
2) allows up to 50 watts of power output, increasing range (but most handhelds only put out 4-5 watts max)
3) can use repeaters to increase range even further
GMRS drawbacks:
1) requires a license for use (no exam; just a fee)
2) range for a handheld radio without a repeater isn't much better than MURS
3) repeaters are very scarce (Utah has only 6, for example)
4) only 15 channels available (22 on hybrid FRS/GMRS radios)
Ham radio benefits:
1) has far better range than all the above options (50 watt output is common for mobiles; some have 75+ watts)
2) handheld ham radios can use upgraded antennas, further increasing their range.
3) thanks to repeaters, the range gets even better (especially with linked repeaters)
4) repeaters are very common (Utah has 129 on 2m and 179 on 70cm)
5) ham operators tend to be much better behaved than CB operators
6) ham uses FM operation for clear sound
Ham radio drawbacks:
1) you must earn a license by passing a 35-question test
2) equipment costs more; a quality 50w 2m radio/antenna/cable setup runs ~ $225
3) because of #1 and #2, many Jeepers don't have a ham radio
Once you've had a taste of ham radio, you will forever look down on CBs due to their significant shortcomings. But does that mean CBs are entirely worthless? Of course not. If all you want to do is talk to other vehicles in your caravan and you'll always be very close to each other, CBs would be a simple, cheap way to achieve your goals. On the other hand, if you're really thinking you may be in a remote area with no phone service and you might need to make an emergency communication with the outside world, CB will very likely be completely useless in such a situation... and if you're counting on it to save you, you are setting yourself up for disappointment.
In summary: ham is the best method for Jeep-to-Jeep communication. If for some reason that just isn't an option for you, CB is likely to be your next-best choice.