For the same power output a brushless motor will be smaller than the equivalent brushed motor, the brushless is also more efficient so less input power converted to heat. Brushless outrunner motors generally provide more torque so can turn a larger propeller. While brushed motors can be used you do have an inefficient lump wasting battery power (most brushed motors are still using ferrite magnets which are bulkier and much less powerfull than the Neodymium magnets used in brushless.)To some extend I suppose that is the same as choosing an old cast iron car motor or the modern aluminium castings of a modern motor. ould you rather have a much heavier iron lump in you car or a more powerful lightweight engine (classic car enthusiasts need not reply).
Jim
