Also, the suspension makes a big difference on uneven terrain. My opinion, and many will disagree, the KW 8 bag suspension is not that great. The Volvo/Hendrickson Z bar air ride is actually half decent at articulation.
The gold standard in off road performance is a walking beam/ Mack camelback design, but they come at a cost of ride quality. Neway used to build an air ride that could keep up with a walking beam, but it was heavy and maintenance intensive.