It's the gray Graupner I have on the TT, It's ok because the plane is so light and the engine pulls it around just perfectly.
I have had many APC props and I know that they produce great power.
I guess APC and MAS is a tradeoff between durability and power, I choose durability as planes anyway tend to be overpowered for anything else than advanced aerobatics & 3D flying which I don't do anyhow.
After takeoff I usually fly around at half to 3/4 throttle and have little use for the extra thrust an APC would provide.

I think I'll order Master Air Screw K-series, 13x8 for my .70fs and 14.8 for my .91fs....Sound reasonable?