I have had a good bit of experience with this debate here recently. I have had the 2-way radios for some time and I have a real hard time hearing them over the diesel noise. They work pretty well when you are in a small group of trucks that are close together though. My K-40 CB took a crap on me out in Moab last month, so I borrowed my friend's hand held CB. It was an older model, but I was VERY impressed with it for what it was. I could hear it easily, and we transferred it between trucks with no issue. That said, more than half of the trucks on each ride had Hams and with the size of the groups and how far we were spread, you can begin to see why HAM is preferred on those type trips. Rubicon and Moab are HUGE by comparison to our runs and the various trail leaders used the HAMS to find out where the other groups were, needed parts/help, etc. The bigger our groups get, it might be wise for the head and tail of the group to have HAM, and if we have more than one group, same deal. Imagine Uhwarrie with a "stocker" run and a Kodak run. The trail leaders could easily cooridinate meeting points, times, etc.
That is why I invested the nominal time to take the test and buy a handheld and mobile radio. We tried to get in touch with the "stocker" run this past weekend and never did get anyone to reply until they entered the camp.
The 2m handhelds can be had for under $150 and with 5-7 watts of power, can transmit clear/clean for a great distance...