[Espeefan]

Brushless motors are more efficient then brushed motors, with similar performance specs. I use the term 'similar' lightly because it is almost impossible to do a direct comparison between the two motors. They are so different in construction, and in the way they operate. One of the biggest things that make brushless motors more efficient is the simple fact that they do not rely on brushes to energize the armature poles, or windings. Brushes produce drag (rotational friction) on the motor's commutator and waste energy. Brushes wear with time, reducing efficiency. Spring tension on a motor brush grows weaker as the brush wears also. A brushless motor's only rotational friction comes from the shaft bearings, and brushless motors do not loose efficiency with time, as long as they are run within rated current and voltage specs. Heat is just about the only enemy, as it is for any motor. Brushless outrunner motors also produce much more torque by design. The motor can has multiple magnets inside of it, and most outrunner motors have more poles then a brushed motor. Most brushed motors have 3 or 4 poles. An outrunner usually has somewhere between 6 to 16!

To say run time is longer with a brushless motor vs. a brushed motor could be true, but in theory a brushless motor can have a short run time as well. It just depends what you demand of it. The important thing to remember is the amount of work that the motor can do. With a brushless motor being more efficient at converting electricity into torque, there is less wasted energy, hence more work being done.