wrote
The only reason to use a 3 bladed prop is to reduce ground clearance.
Every other thing about them is bad. Reduced thrust for the same RPM of a 2 blade prop is the biggest factor.
When you have more blades, each blade is working in more turbulent air, from following the other blade. The most efficient prop is a one blade prop. Yep, I'm not making it up! They are made with a weight opposite the blade to balance the system.
They are usually used on indoors free-flight rubber band models, where the PRM is low, and efficiency is the most important factor in winning.