I have a c5, a c5 and a Hurst. I can't find a freaking knob for the c6, but it isn't that much different than a c5, diff angle/ergos as mentioned above. The Hurst is adjustable, and on the wimpy setting, it too much for me. The ergos on the c6 apparantly are great. It would be good to try to put all that ergo stuff on the c5 hurst, and find some super wimpy springs....
Big thread on another forum showing the diff b/n all 3.