More solidity, less efficiency, is correct.
Generally speaking, the more blades, the less efficient the propellor...for cruise.
Of course, a whole lot depends on the blade cross section, width, length, rotational speed, etc.
Take a Cessna 182 as an example.
Two varieties of propellor are offered, two and three blade.
Three blades would be desired if maximum takeoff/initial climb performance was of importance.
The two bladed propellor would however, generally produce the highest cruise speed (a knot or two) provided the same engine conditions were met...BHP and rotational speed.
To maximise the speed increase, the lowest usable RPM would be desired.
Reason?
Less drag due to the fewer number of blades.