The combines as in the threshing, separating, & feeding are identical in every way on the 2010 models. The 9120s of the past have come std with the xtra fine cut chopper, now that is an available option on the 8120, but it takes alot of power. I just talked about this with my dealer, and from real world experience a chipped 8120 can put more product through than a 9120 but that does not take into account grain loss.