In the following video you can see two available control modes in the Smart Motor Driver, the first one is direct pwm control. So the motor reacts immediately to any change made by the user. In the second one is PID control mode, here the controller calculates acceleration/desacceleration to achieve a better and safer control of the motor. The changes are not immediately but are better suited to prevent damages like flipped robots, stripped gears or even battery cut-outs due to overcurrent.
See by yourself the improvements, the best of all you don't have to do anything complicated thanks to SAMI capabilities.