The very first run shows the power difference quite well. The F10 M5 gets a jump and the M6 has to run it down. And run it down it does as it quickly catches and pulls far past showing the power disparity. In the second run the M6 gets the better launch and the race is over right away. the M6 simply puts bus lengths on the M5.
The new F13 M6 is faster than the F10 M5 stock for stock. With modifications, it's no contest. The PP-Performance modifications are definitely making a substantial difference and that is a very quick M6. Check out the video with runs from a stop and roll below.