I read from another post the new models have the following differences: "The drive system is different, the new units use ZT series axles with spin on oil filters.Y ou have new gas tanks with sight gages and larger gas cap's, a rubber discharge chute, more engine options, taller thicker rear bumper, seat with a slide adjustment and a thicker frame." Is the ZT (2800 I believe) with spin on oil filters (not sure if I understand this) a big improvement over the previous model? Sure sounds good. How much thicker is the frame? I'm looking at either a non-current 20hp Kohler Command/52" or new model 19hp Kawasaki/48" for about the same price and I'm trying to decide.