MAS and APC don't measure Pitch the same way. An APC 11-7 would act more like a MAS 11-8 or 11-8.5 Or conversly the MAS 11-7 is more like an APC11-6 or 11-5.

All I know is on engines I run over 12K the MAS seem to work better on engines I run less than 12K the APC's seem to work better.