No, it's not me saying it, although it could as well have been. It's the two guys in this video:
Shooting a DSLR and a Mirrorless on the same job. - YouTube
The video is a slightly boring conversation, summing up a shoot done with a D800/70-200 and a GH3/35-100. They did not comment on image quality, other than saying that both cameras provide stellar stills as well as video. What we know is that the D800 delivers more on the stills side, while the GH3 is the master of video.
The interesting part is when it comes to how the cameras work in a real life, particularly when doing hybrid stills/video shooting...
There's another thread here, called "What, no activity....?". This, I think, is part of the explanation.