Torquer-- no a bigger spur doesn't turn slower, if the r=gear ratioa are the same.... 4:1 is 4:1 period, the motor pinion will still spin 4 times per revolution to every 1 of the spur.... and if the spur takes less power (torque) to turn over the spur the big spur car will actually accelerate faster, and could potentially have higher top end if the motor doesn't have the torque to push the spur past an RPM level that below the maximium RPM of the motor.......
That being said I also agree that the tc3 and most tourers for that matter don't have enough adjustability in the spur/pinion sizes to make enough difference..... now if it was possible to mount a 69 and 98 tooth spur on the car then we could do an actual test that would prove something....... but from 69-75 all you get is enough to "fine tune" you ratio, which isn't a bad thing either!