Bad photographic decisions, usually exposure and lighting, and bad post processing accounts for all of what most people think is the difference between using m4/3 or full frame. m4/3 isn't as tolerant of underexposure or overexposure, and that's almost the entire difference that I've seen, shooting systems from m4/3 up to medium format backs. In my experience, there's about 2/3 of a stop less forgiveness for an exposure miss in m4/3 than in full frame, if the eyes looking at the image are those of a good (but not professional) photographer.
That people in this forum think that the problems and differences seen in the images above are because of the format means they haven't spent much time looking at full frame images from photographers who don't pay enough attention to technique… There are full frame shooters - some of whom think they're pretty good - whose images would convince you that m4/3 was superior.
If you can see the difference on a computer screen, it's almost certainly exposure/lighting issues, computer screens are so much less sensitive than printed images. But if a photographer has worked on skills and shoots with discipline, even image processing professionals couldn't tell the difference.
In the case of the two sets of photos, anyone who believes they can see a difference between the shots with the 5D and the m4/3 camera is suffering from viewer bias. If the pictures were shuffled together, and you were able to correctly identify 80% correctly which camera made which image, we'd have the beginning of a conversation.
On many travel shoots, I shoot a combination of m4/3 and a Nikon D800e, and at my last three shows where I had images printed around 20x30 (varied based on aspect ratio of the image), no one who thought they could tell which image came from which camera was better than a random chance at correctly identifying which image came from which system. On a few images I had to pull the files up on my laptop to show people the EXIF data to prove the image was shot with a Panasonic G3.
If you miss your exposure by more than 2/3 of a stop, or stand subjects close to intensely colored walls or in open shade, or mix lighting sources with different white balance, or can't hold your camera steady, none of those have to do with m4/3.
Once you get to m4/3 size sensors, if you think that the sensor size makes a difference in your success producing good images, you're not taking responsibility for your own results.
It's amazing how much better my images got when I decided any problems were the result of my own actions.
