Actually, among higher lever TCs, belt driven ones are typically smoother. This is because of the more efficient transfer of power from the motor to wheels, i.e. cars with drive shaft would have to convert sideways rotation direction of the motor/shaft to forward direction.

The sideways rotation also affects steering in a well balanced car, which is not the case on belt-driven cars.

Because of this and the increase in belt durability, more and more companies are converting their pro level TC to belt. For example, the TC5 is belt driven where as previous generations were shaft driven.

Also, the fastest RC is based on the belt driven MI3

Anyway, shaft is good too, especially for bashing, drifting, driving on asphalt/outdoors since the drive train is mostly (except for spur and pinion) enclosed.

Nice build so far, I want to see how fast you can push that thing.