Something I would like to add, I have run brush motors in the past, 05 modified motors, d4, p94, d5, speed gems, I ran a plettenberg 290/30/4 at one time, 700bb 8.4, I was able to get GPS reading with some of the motors, running nicad cells. I also had a lehner basic 4200 back around 2002 which I ran on nicad, years later was able to run other size brushless motors on nimhs. And had GPS reading with nimhs and brushless. In my experience the brush was right there in speed to the brushless on nimhs cells. I have melted many 05 end bells on cheap nicads. Setups a little over 200 watts of input power melted 05 endbells. I have burn can 540 at far less input than 200 watts. Where the brushless shine is the ability to handle far more power than a brush motor would handle. So with the power of today's battery the brushless can run bigger props for a give kV and motor mass than the brush motor thereby being faster than the brush.
Example I can run a x438 with my 5050kv 2860 motor on 2s.