Back by popular demand: Nex-7 vs OMD

A shot with same aperture, same shutter-time and same ISO should get the same "brightness" or exposure.

The positive effect you get from "bigger-pixels" (looking at the Nikon 3Ds) is that ISO 1600 or higher ISOs are still looking good, while ISO 1600 or higher ISOs on m4/3 is not so good...

The bigger the pixel, the more photons will fall on the pixel. Even in dark areas photons will fall on pixels! If you have very small pixels, you have the possibility, that very little or even no photons fall on the pixel. These very black pixel get less picture information and can't be pumped up by the ISO very well... (because of this you see the noise first in dark areas)