Mike, I didn't expect an answer _this_ simplistic from you. Here's my take, Kennith-style; Mike W will likely respond in about a week with something "for Chrissake, a radio is a radio" (all in capital letters), and he will be right.
First, quality: both CB (AM) and 2-m ham (FM) use 10kHz bandwidth. It translates into roughly 4kHz of usable audio band, and therefore the quality should be the same. In absence of static, it _is_ the same - I'd even say I like my $40 CB unit better. Here goes "2 meter naturally sounds much better."
Next, range. A typical 2-meter mobile unit has 50W transmitter output, and the antennae are shorter (in terms of fraction of a wavelength) than CB - giving a ham mobile transmitter a huge advantage in power density (Watts per steradian). However, there are three disadvantages I can think of:
- 2m is much more of a line-of-sight communication band than 12m CB, although you can get pretty far on the fringes of diffraction/refraction pattern; you can get very long-range reception with a CB box and tuned 4" Firestik;
- narrower directional diagram of an antenna means more frequent loss of communication when your antenna is slanted (which happens off pavement) or your other party is at a significantly different elevation than you (which also happens);
- the noise figure of a receiver at 2-m band is typically worse than that at 12-meter.
I am not going to talk about the additional benefits of having a ham radio - like using the repeaters or APRS or [insert your particular joy of ham license].
But, to sum it up, for trail use I have not yet found any considerable advantage of using ham radio - except for handhelds. FRS? meh. Kevin is right on the money here.