ORIGINAL: brett65
My personal opinion is that if two blades were actually more efficient then you would see them on all modern propped aircraft. It depends on the use and application. The alpha 3 blade prop is purposely made to be a slow prop, its on a trainer. I got a 10x5 3 blade I'm gonna try on my Extra 300.
3 and 4 blade props are used on full scale aircraft to make use of the available power from the engine(s) where a suitable 2 blade would be too large for practical use.