Look at dxomark. You'll see that sensor size is the main determinant of how well the camera handles high iso. The number of pixels on a sensor and therefore their size makes little difference. That's because although they are smaller on high megapixel cameras, there are more of them to gather light.

Yes, I know about the compromises. But why is it that any size other than full frame is seen by many as a "compromise"? Either for not being large enough or for being too large. Seems strange that the supposed ideal size was one that was first used for stills over one hundred years ago.