how comparitively densely populated are 4/3 sensors compared to larger common sensors and what advantage, if any, there is in it.
E-M1 Mark ii, 20mp, pixel pitch: 3.32 µm
Nikon D850, 45.70mp, pixel pitch: 4.34 µm
Pentax 645Z, 51mp MF, pixel pitch: 5.32 µm
Theoretically, the differences are:
- smaller pixel pitch = diffraction at wider apertures
- smaller pixel pitch = better low-light performance
- smaller pixel pitch = smoother tonalities, less noise
- allows higher MP counts
- higher MP counts require more demanding technique to perform optimally
- higher MP counts tax storage and CPU/RAM/computer resources
- smaller pixel pitch = more heat, harder to cool off
Practically speaking, a lot of this depends on the manufacturer's implementation, and print size. At 8" x 10" prints, you probably won't notice a difference. At 17" x 22", I've found that the differences between an E-M1 and D810 can be pretty subtle. Bigger than that and it's more obvious... though your viewer will be further away.
IMO single-shot 50mp for M43 will have too much diffraction, too much noise, and will require stable tripod or strobe to get the most out of it. If you really need that much info, you're probably better off with 35mm sensors.