I think you will find top speed is more to do with the airframe than the prop. I say this from past expierience. I had a plane that was old faithfull. It was a SuperSportster .60. I flew it many, many years. I always hated trying a new engine/plane combo. So I would break in the engine and test fly it on the SS. That being said I broke in a ST.75 and several ST.90s on this plane. The bolt patter was the same as the ST.60 so why not. What I found was even with the .90 it wasn't much faster. The big difference was when you pointed it up. It didn't slow down with the .90 on it.
Pitch difference in props is another thing. I have a Saito .72 powered Pizzaz. I have run an APC13x6 and an APC13x4W. The 13X4W has instant throttle response. It is better for short takeoffs and hovering. The 13x6 tranfers a little slower but has better top speed. On this plane however the higher top speed causes flutter.
I hope I am not confusing the issue for you. Let me finish by saying I ran a ST.75 for three years on a Ultra Sport .60. The 13X6 Master Airscrew was the best prop for it. I flew it as a sport/patter type plane. If I had wanted more verticle I would have tried a 14X4w. I guess it depends on how you want to fly it.

David