I was told that spring suspensions on zero-turns doesn't really do much for ride, too stiff. AND, how could you keep cut even and not scalping if the machine moved up/down all the time, like would do on my rough yard? Most didn't have shocks, but see more now having those with springs over. I was looking at Simplicity's last summer too, think they are pretty good unit for the money. SO many models any more, hard to pick one to be happy with.
My neighbor has a zero turn and I adapted a pair of Sears seat springs onto it for him. He mows about 12 acres with it.