Dyna Vt or a Dyna step???? It is just a difference in computer programs, the VT is a step above. In any case you'll love the Cvt. The 8.4 Sisu I believe is a good motor. I traded an 8460 to a 8650. I would say make sure it has all of the updates on it. If you have a good Mf or challenger dealer nearby, there will likely be a few electrical glitches as in all of the new tractors. It will likely be cheaper , Try to demo it and compare how it pulls. Once you figure out the buttons and settings, it is pretty sweet to drive, no comparison to a powershift. Again a good dealer helps.