I think I'll jump in with what I do and why.
First I need to say that when it comes to my hobbies I can be really OCD.
I run all three, CB, Ham, GMRS. I got into CB in the early 70's before it became popular and got my ham license later. I have been using both off road and on road my whole life. By the 80's I had learned how to tune antennas and had experimented with CB and ham to find what worked best, where on my vehicles.
After decades of running in groups, in everything from dry lake beds, to narrow canyons, 2m with a center mounted 1/2 wave antenna won out. CB would have been better except for the noise level killed distance. The advantage of the 2M is the wave length. It bounces off things. I can go around a corner in a tight canyon and still talk. The advantage of the 1/2 wave is the signal comes off flat where as a 5/8 wave goes slightly up. Sitting several miles apart on a dry lake, swapping diffrent antennas, this becomes obvious.
Side note: I played with 10m mobile, 11meter (CB), 2m, 70cm. Antennas 1/4 wave, 1/2 wave, 5/8 wave in varying lengths, coil types and position on vehicle.
Two years ago GMRS started becoming popular and I started comparing. GMRS is in the 450 meg range. The wave doesn't bounce as well as 145 meg (2m) I already knew this from the 70cm ham band experiments. I played with a 6db gain half wave and a 6db gain 5/8 with the same antenna results as 2m. I run GMRS in my rig because most of my new group does. When we lose each other due to corners and sometimes tight woods, I am still able to talk to the other end of the group with 2m.
In the last 6 months out here, I have been monitoring GMRS on scan on the weekends. I hate to say this but what I hear is what I heard in the late 70's when CB became a fad. People being rude.
I'm not against GMRS and due to the noise level in CB, GMRS wins out over CB. There is no comparison to 2m though. In my opinion, off road in general 2m with as long of a 1/2 wave antenna you can get wins out. I'm not counting repeaters because, lets face it, their repeaters. The areas I go wont have repeater coverage.
As for 146.520, that's on my second band all the time. I hear people there more than any other but, as someone already pointed out, NO radio is any good if no one is listening.