There may be something I'm failing to grasp here. Firstly the difference in resolution arising from the camera is down to number of pixels, not the frame size - I'm comparing GH2/GX7 16 MP to 5D2 21MP and also the " per pixel sharpness" although I have no idea what factors shape that. The frame difference just results in bigger pixels which are one determinant of overall signal/noise, i.e. how noisy at higher gain settings. Right so far?
Therefore a M43 lens needs to resolve more lines per mm to compensate for deficit in pixels, not size of pixels - Yes?
So the fact that the Leica/Panny 45 peaks just over 1500 and falls to about 1200 at edges at 50% contrast whereas the Canon starts at over 2200 and declines to about 1700 at edges suggests it's a lot better?
However, in the real world, the Leica Panny may be good enough. In reality in 3 and a half years I've really only used the Canon as a portrait lens - I think what I plan for indoor still life more equates to product shots, in which case the Sigma DP3M is a better tool anyway. The 45mm would, I think, be a good field macro lens though in conjunction with the GX7's tilting EVF.
I think I may do this and go with the Olympus 12mm at the wide end. If I find I still crave an ultra wide occasionally , there's always the Olympus 9-18
Sorry for boring you folks.