Not really, most discs tend to have a better hold than rim brakes, so an extremely heavy motorbike on top of a magura hs33 isnt gonna work.
And you said earlier in that post, that an avid bb7 works worse than a rim brake, I don't know what bb7 you used, but the bb7 is arguabley the best disc brake out there for push trials bikes (the hope mono is also known to be good)
Anyways, disc or maggy is a hard question, and at the end of the day its personal preference. Discs have their advantages vice versa, i use a maggy but will admit discs are far more sutied to my riding. Wish I got a rear disc echo now, as i like to ride in the rain and hate the maintinence (sp?) from a maggy.
There is nobody who can say 'discs are better' and nobody who can say 'maggys are better'. All personal preference...
And discs are quiet.. You gotta love a quiet brake!