Full scale aircraft use multi-blade propellers to absorb, and make use of the power produced by very powerful engines. They also turn the multi-blade props at much lower RPM,(using gear reductions) with much higher pitch, than a model engine will be able to do.
If you can reduce the prop speed on a model engine with a gear reduction, then you can turn a multi-blade with much more efficiency. Such as with a RCV engines that use a 2:1 gear ratio and recommens higher pitch. When you slow a prop, you need more pitch to get comparable speed. Pitch produces speed, and diameter produces thrust.

I have compared 2 & 3 blade props directly in a model several times. Always need to reduce either diameter, or pitch to get the same RPMs with a 3-blade. As result you will loose either speed or thrust, for a given situation. By increaseing engine power you then run a comparable 3-blade with a as much effeciency loss. That the "real world".