Okay, here goes. Hopefully someone will confirm this for me....
1. The Super Blackhawk, except in the 5.5" barrel length, has an unfluter cylinder, which makes it heavier and thus more controllable while firing the .44 magnum.
2. Whereas the Blackhawk has an aluminum gripframe and ejector-rod housing, those parts on the Super Blackhawk are made of steel. That adds a little more weight, and thus a little more control. I want to say, however, that on stainless Blackhawk models, the grip frames and ejector housings are steel instead of aluminum, which accounts for the slight weight difference between carbon steel and stainless Blackhawks with identical chamberings and barrel lengths.
3. The grip on the Super Blackhawk is much larger--it's designed to be a lot more like the grips on the Colt Walker and Dragoon cap 'n' ball revolvers, the powerhouse revolvers of their days. The pointy-bottomed trigger guard on most Super Blackhawks is an homage to those old Colts.
4. Blackhawks are only offered in 4.75" and 6.5" barrel lengths, while Supers come in 4.75, 5.5", 7.5", and 9.5".
BUT, there is now an exception to this convention: the newly-introduced Blackhawks in .44 Special. These are built on a smaller frame-size than the Blackhawks and Super Blackhawks, and use a steel grip-frame that is borrowed (like the frame for the body) from the New Vaquero.