ORIGINAL: eddieC
For our models, there's little difference.
From a design & efficiency standpoint, the fewer the blades, the better. The primary reasons for number & diameter of props on full-scale is prop clearance and keeping prop tip speed below the speed of sound (big loss of efficiency).
There is another reason for multi-bladed props for full-scale. Matching the blade area to engine power. It is also a clearance consideration sometimes. However, it's primary reason is needing more blade area. The 7 blades on some turbo-props is a perfect example. Imagine the diameter of a 2 bladed prop with the same blade area. And of course, as you mentioned, imagine the scream from those 2 tips.
In WWII, most of the fighters got more blades as the war dragged on. They were getting more powerful engines usually. The P47 was one that wound up getting 4 blades and then getting wider 4 blades. They called them "paddle blades".
Model speed flyers have flown 1 bladed props off and on. They read that fewer tips were more efficient. The popularity of 1 bladed props shows how important that efficiency isn't.