the APC 10x4 is also a good combo, but it revs high and dosn't give the most power in the hang, at zero airspeeds the Master gives better power, plus because its a bit crap you can go up an inch in size compaire to the APC which bites like hell. above 5mph ish the Master looses it's advantage and the APC wins, thats why i went with the 10x4 for the climb and glide. rest of the time its the 11x4 for power in the hang.
case in point... my cougar on the 11x4 vs a irvine 39 cougar with a 10x4 APC, i can pull out of the hang easily, the other has to hang on more RPM and pulls out slower, also has less control.