I'm not going to go near stills image quality differences because I don't believe there's more than the most marginal difference between them, after viewing lots of Olympus raw files from the E-M1. How you shoot, how accurately you expose and how you post-process has far more impact on the final result than anything intrinsic in the sensor itself. I've used Olympus and Panasonic side by side for years and any differences there might be between the two, in terms of IQ, are minimal.
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