I,too think off-road would be worse. If you really wanted my opinion. It's the nature of the beast. When I drive my Maxx, I'm always hard on the throttle. And I'm always looking for something to pile over. Something to jump or climb. By it's very nature, a monster truck is designed to beat the piss out of. Hence the reason the term "bash" is used when we all get together.
An on-road is all about speed through finesse. Yeah, they break. Chance meetings with curbs, lightposts, mailboxes, and other things will take them out. But I don't go out with my RS4 3 looking to clear large, heavy immovable objects.
And if the guy at your LHS breaks his on-road more than his Maxx, he's not driving his Maxx right...