What is the mechanical load like? Does the motor see a constant torque like a reducing gear box? Does the load start out as a stalled load like an air compressor starting up against a pressurized tank? Does the mechanical load take a long time to come up to speed? Will the mechanical load backdrive the motor?
What kind of duty cycle will the motor see? What kind of environment will the motor be in? Constant high or low temperatures, wet or dry, dusty, high vibration, run to fail or preventative maintenance, external or internal fan cooled.
What horse power range? 1/4, 1/2, 1, 3, 5 HP?