As far as i am concerned, the 4" pitch props are for pure 3D or funfly type flying only. I tried one on my F90 and didn't like it. As far as thrust goes, the 16-4W pulled exactly the same as a 16-6. The difference being the 16-6 had a bigger speed envelope and the thrust started coming on at a much lower rpm. The 4" pitch props only work well when the engine is really turning up. A friend of mine tried a 14-4 on his Saito 65 and nearly crashed his Martha. That was because the throttle needed to be at half or more before it had any pull. He wasn't expecting that and caught it just in time from a spin recovery.

Also, pitch numbers are only relative within a certain range of diameters. As you go with bigger engines and larger props, the pitch numbers increase also to give you the same effective pitch or blade angle. In the 16 and under range, 10" pitch is a lot. In 24 to 32 inch diameter, a 10" pitch would be very low and maybe not available.