I can't think of a condition where the current 55" Lexion or Deere is not going to have significantly higher capacity (say 2x or more) then the 7700 of the same width.    If you can, I'd like to hear what it is because it sounds interesting.  It has been my personal experience that in the conditions we normally encounter nearly every machine on the market suffers from insufficient horsepower.  That is the first major difference..7700 was 140 hp or thereabout, the Lexion is more like 400.  Then there is seperation....the rotary seperation is much more capable then the short straw walkers were if seperation is limiting.  Grain handling of course is easily handled...just make the augers and elevators bigger and they will carry the grain. 

I guess I do not agree with the contention that cylinder width is valid as an absolute measure of capacity.  If it were, we would not have seen this width machine grow from a class 5 to a class 7 over the years.