Just thought I would add my 2 cents.
I am a long time ham who has designed/ built/ sold & installed police/ fire/ EMS medical/ and mountain top repeater radio/data systems.
In the end there is only slight range differences between FRS/GMRS & MURS portable radios. Not much difference between 1 and 5 watt hand helds, except for battery life. If 1 watt cant talk, then 5 watts won't work any magic. Cheap FRS/GMRS radios come in last- you get what you pay for, and there is a bazillion co-channel users with $29.00 FRS/ GMRS radios. There are times when FRS/GMRS frequencies will out talk VHF/MURS, then there are times when the opposite is true. Predicting radio waves is both a science and an art. The closer to line of sight (the source of the bogus 30+ mile advertised range), or direct bounce you can get the better.
27 Mhz. CB radios just plain suck, unless you are talking short range to truckers or your neighbors. The expensive ones just have more noise reduction circuits & better microphone processing, or just more lights, switches & chrome. They cannot really talk any further then a good $50.00 radio with a good $50.00 noise canceling mic.
UHF (FRS/GMRS) frequencies don't like pine tree covered terrain because the needles resonate 1/4 wavelength to ground. But it are slightly better at bouncing around in tall/ concrete buildings, metallic structures, cars and rock covered mountains.
VHF (MURS) frequencies don't like tall/ concrete structures that much, but do "bend" a little better over rough terrain in open country.
Repeaters UHF or VHF (fixed tower or portable) are the best for miles covered when placed high or in the open between users, but require $$ & coordination.
IMHO - MURS frequencies (151 & 154 Mhz.) have the advantage of good outdoor coverage, neat products like murs-radio.com sells, and is close enough to the 2-meter ham band (146-149. Mhz.) which has free "open", and "closed" club repeaters all over the country. They will be VERY active if T.S.H.T.F., and are good to listen to during local emergencies because the hams will do all the police/fire/ FBI scanner listening for you. Many of the upper grade radios now include switchable voice inversion scramblers programmed in to approach voice security (makes you sound like Donald Duck talking backwards to casual listeners).
The secret to great usable coverage is not in the watts transmitted (an overrated measurement in my opinion), but in
(1) Closeness to line of sight between units or repeater,
(2) the quality and gain of the antenna, cable & connectors used (YES- upgrade to a gain type rubber-duckie on your hand-held, especially effective on VHF/ MURS frequencies), and
(3) the quality of the radio. Look for better specs in the Rx- sensitivity (lower# is better), co-channel, & image rejection (higher Db # is better), & low audio distortion %. Also low standby battery drain (low MAh drain # is better). Tx- spurs, harmonics (bigger negative Db # is better) & low audio distortion %.
Think about good police/ fire radio systems - portables usually cost $500.00 and way up, base stations & mountain top repeaters have 1/2 to 1 1/2 inch hard-line coax with silver plated connectors leading to an antenna costing over $1,000.00.
Hope some of this helps. Glad to answer questions if I can : garysco (at) gmail.com