I believe a car is only as good as its driver,and what they are used to.
Ive raced both belt and shaft driven cars, and will say the belt driven feels smoother,which could be an advantage on a slippery track,but then you could always dial that in with your speed control, to a certain degree.
Ive stayed with the tc3 for quite a few years,maybe I prefer the on/off "snappy" power of the shaft driven car,some people prefer the smoothness of the belt driven cars.