My duece fiddy gets the job done. The 6.7L hauls my skid steer with a mulcher on a 20+3 trailer up the crappy mountain dirt road. I can't tell you much about the others but mine works so there is that. It's also super comfy. When I hurt my back last year getting in and out was better than getting in my wife's suv and the truck seat was the only place I could actually get comfortable outside of bed. It isn't necessary to keep the def parts. From what I hear.