I think the best comparison I've heard is that in the RZR, you avoid hitting the rocks and stuff. In the truck, you just go WFOT over and through everything.
Thats pretty true but because of that the parker race multi laps just beat the shit out of me in the truck .. when I was out practicing I had the truck and the RZR when I got out of the truck and in to the rzr I was pleasantly suprised at how fun and agile the rzr was