Well, I only cut small grains, but here's my take (I have a pair of 1680's, almost twins but 1 has a specialty and 1 has a standard)-
The Specialty Rotor is definitely more aggressive. Tough conditions, it thrashes better, and we normally run it 2-300 RPM slower to get the same results. Tears the straw up more. But, we have had more trouble getting whitecaps out in the past, so I run a full set of Gordon bars in it to make it perform more like a standard.
An AFX has the same bars as the specialty. While I don't run one, I have Kile fronts on the other two combines, a pair of 2188's with standard rotors. WAY less rumble in tough crops, feed nicer, and appears to be cleaner samples than with elephant ears. So personally, while I think the front of an AFX is probably a good deal, I'd end up putting Gordon bars on it in my conditions, to make it more like a standard.