Threw together a quick test video comparing the sound differences between 6 bladed props, 4 bladed props, 3 bladed props and standard 2 bladed props since it all kind of sounds the same when flying, you never really get to hear all of them at once. So  i start the video off with all of the audio at once, then switch from channel to channel twice, then play back each flight.

So far, the biggest difference I noticed was that with the more blades the higher pitch the sound of the blades chopping through the air, the 6 bladed props were slower to respond, might be good for aerial video/photo, the quad and tri blades seemed the most responsive, followed by the bi-props in response.

This is all indoor obviously, so some vortex ring state and prop wash can be seen when closer to the ground, so i would like to redo the same test outdoors when i get a chance, maybe get comparison for different things like hover, flyby audio, and maybe some onboard audio as well.