I agree that lipos will result in better performance for almost any plane. But a brushless motor is not required in order to benefit from a lipo.

Assuming the motor will work properly on the voltage provided by a lipo, the benefits of the lipo's lighter weight and better power-to-weight ratio will be there, regardless of whether the motor is brushed or brushless.

Brushless motors have their own advantages, of course, and the combination of a brushless motor AND a lipo is best of all.

- Jeff