Aviation Consumer did a feature article on this a few years ago, using several different airplanes and props. Their conclusion was that the 3-blade props generally provided slightly faster climb rates (roughly 5%), at the expense of a few (2-5) knots lost in cruise speed. The 3-blade props were definitely smoother (they measured vibration levels at various power settings), and almost all of the participants and observers thought the 3-blade props were substantially less noisy than the 2-blade. The 3-blade props also provided more 'braking effect' when power was pulled off. But overall, the 2-blade props were slightly more efficient in cruise, where we spend most of our time.at7000ft wrote:Concerning a 3 blade prop on a Panther. Is it true that only advantage over a 2 blade is that it looks real cool?
Interestingly enough, when they actually used a decibel meter to measure the prop noise (both on the ground and in "flyover" mode), the 3-blade props were actually louder than the 2-blade props. Apparently, the difference was the frequency of the noise changed so that it occurred in a range that is less "objectionable" to human ears.
But the "ultimate" quality that won the day for the 3-blade props in the Aviation Consumer review was the "cool factor"... Everyone agreed that the 3-blade props just looked better, and made the airplanes look fast just sitting on the ramp.
One other thing to consider if you're going to be flying a lot of aerobatics... The gyroscopic effects of a 3-blade prop (generally heavier than their 2-blade counterpart) will be greater, and will thus transmit more loads/stresses to the engine, engine mount, and airframe during aerobatic. Just food for thought, as I have no aerobatic flight experience and am not a load stress engineer.