I'd go with the 2-blade
I've had my Vision 32 since 1990, and have always been more than satisfied with the 2-blade. The boat does 7 knots at 2800 rpm in calm wind/water conditions, with plenty of reserve power for worsening wind/wave conditions. It has excellent thrust, and even backs relatively well.If your Vision doesn't have this kind of performance, I would suggest having a good prop shop repitch it.IMO, the 3GM30 is plenty powerful for this boat, and the only thing a 3-blade prop will do for you is cause you to sail slower in lighter winds.