It depends ... Similar to fixed wings, the efficiency of rotating blades depends a lot on the blades L/D, which is very dependant on the Reynolds number. Considering similar disk loading, smaller multiple propellers could have the Reynolds much lower than a single propeller. For a small 2-4 person aircraft, replacing one propeller with smaller ones doesn't make any sense. Aerodynamic distributed propulsion gains are maybe around 5%, but you loose 20% or more on propellers efficiency.Yeah, but has it flown yet and proven that multiple small props are more efficient?
Looks promising. But it will have to get better before they'll sell a lot of them. In terms of seat-miles per kWh it's not good. An electric car does nearly four times better. It can't fly in any precipitation. In terms of fun and efficiency, it would almost be like a single-seat helicopter except for its short range. Range is too limited, like any electric vehicle. In terms of difficulty, real easy to fly. Computers do most of it. But so much fun!To the point about multiple props:
Everything's a compromise, obviously. Small a/c have a hard time fitting enough prop area for true STOL or even VTOL, but it can be done with 'distributed' prop area. (Mission, mission, mission....)
These guys are showing how it can be done: