Sensor based motors are most often used in applications where the starting torque varies greatly or where a high initial torque is required, such as in a RC car. ..blah blah.... Sensored brushless ESC motor systems always know the position of the rotor. This is especially critical at low speed as well as at the start condition when there is no rotor movement. With the proper rotor position information, the ESC can apply power to the correct rotor phase combination.