Actually, my wife and I both feel that mowing in low gear is a more enjoyable experience and provides better results. We just noted that the 7610 was much harsher than the 445 when pushed.
We thought about getting a ztr quite a while ago, but was not the casual and laid-back mowing experience that I enjoy. I spend all day dealing with frustrating employees, clients, contractors and phone calls and need a break. For me, mowing with a tractor does that. Plus, the ztr's ride was absolutely horrific at fast speeds! Hehe, maybe I need to be better about rolling the lawn!
It certainly makes sense that frame stiffness is more the cause of this than wheelbase differences.