The pro4 diff design is far more efficient than any other shaft brands available. Other brands have more gear noise and fragile issues as far as stripping is concerned.
You seem to be so sure about that, have you ever tried or owned another shaft car?
I have a SDW and its more quiet than my TC4, the hollow CF shaft and the light aluminium input shaft makes it also a very efficient drivetrain
also a part from the TB evo 3 that had big issue with stripping gears I dont know wich fragile cars you talking about..