Surface permanent magnet-type vernier motors with three magnet array-type rotors (parallel magnetized type, repulsion type, and Halbach type) are compared based on the pull-out torque. It was clarified that increasing the rotor radius increases the pull-out torque at a fixed three-phase alternating voltage. The mechanism for the pull-out torque increase on each magnet array type was different, when the effects of the increase were analyzed based on an induced electromotive force and a synchronous reactance. As a result, the design of the Halbach-type rotor was found to be especially effective for achieving high pull-out torque, because this array type achieves a large induced electromotive force $E_0$ and a small synchronous reactance $x_s$.