Interesting observation... Especially since I like belt cars
Anyway, I dont think one principal is superior to the other... if it was, all cars would be running it... For the companies it's a lot about marketing blah blah and selling more cars.
I think average joes like me, is best suited with finding out what suit their needs.
For me, it goes like this:
I consider myself as reasonably good in setting up cars, but I'm not that good, that I want to deal with torque steer.
Low maintenance might be an advantage with shaft, but to me there's not THAT much maintenance with a bet car.
Outdoor, a sealed drive train is an advantage. But both shaft and belt cars can do this.
A shaft car might FEEL faster in acceleration, but thing is it doesnt seem to matter on a track when it's about doint most laps.