I was taught:
Less blades makes prop more efficient regarding "screw-through" water.
Also taught, in trade off:
The more blades of a well tuned prop then the less chance for vibration
If there were a way to correctly balance a one bladed prop that would be the most efficient.
Three blade props offer best of both worlds regarding screw-through efficiency and reduced chance for vibration.
I've always wondered, seeing as [evidently] less blades = most efficiency... why IB, direct drive pleasure cruisers don't employ two bladed props. I'm sure with today's technology two blade props can be tuned to the finest of tolerances.
Currently, I'm sticking with my twin three bladers. Good push and no vibration.