Well, I just got off a 300 mile trip (mostly interstate) with my "big" radio and man, what a difference!
The audio is a whole lot better and it's just "quieter" When the squelch is turned up to listen to tx almost out of range it's no where near as "staticy" and abrasive. (If that makes sense...)
I talked to a couple of drivers to adjust the mic gain and power mic and all reports were pretty favorible. The range also seemed to be much improved although this may have been just better audio quality.
Mind you, this is going from the cheapest possible CB to a decent mid-range unit. I can't imagine going from a cheapie to a tree scorcher!
If you can find the room in your ride I say go for a "driver" unit