i was looking at pmr 446 which is an unlicenced band. they only come in handhelds with very limited power compared to a cb. to opperate a propper two way radio you need a licence, which cost more money and comreg have to alocate a certain frequency to the users. a pmr 446 radio pushes out about 500 milliwatts of power, thats half a watt. a cb pushes out 4 watts which is a huge differance. also with a cb you can converse with other members who allready have a set and are not confined to the few that would have their own band.
with a standard cb set up the range is allways down to your location, but recently while testing my own i spoke to a guy on the m1 at balbriggan while i was static outside my house in rush, this may not seem like much but taking into account the geography....ie the big hill that skerries is on, its quite good.
the average 40 ch cb is about half the side of a car stereo and comes with a bracket for mounting, if ye dont feel like drilling holes to mount it some good heavy duty velcro will do.
there are various differant bands depending on what region your in, for example the uk are on a differant set of frequencies then us, to help with this most modern radios can be switched between the regions. so if you see a cb advertised with 240 ch this usually means it can be set to whatever region your in. the frequency range we are in is 26.965-27.405.
the bigger the antenna the better, but you are only as good as the station that is receiving you.
if ye have any more questions ask away and we'll try to answer them