We are combining several very different issues:
The mechanical aspects (basically braking HP/weight)-- a matter of physics!
The "driver" aspects. Some can safely drive ANYTHING anywhere. Others with no mountain experience are very different and need a machine that will "forgive" their mistakes. Add to that that there are a lot of drivers with no mechanical background-- who don't even know that you can't use your service brakes to keep speed down on a long descent in ANY heavy vehicle. Who don't know that brake fluid's boiling point drops with age, etc. IMO the driver is the more critical part of the equation.
Bottom line is there is more to the equation than machine alone.
