A7R owner with no expereince with the olympus, so this is biased...
I agree that the A7R video is somewhat lacking in resolution in this day and age. however apart from that, the camera is faultless. No gimmics like image stabilisation and speed boosters can compete with a true full frame sensor in my opinion. Particularly a 36mpx sensor like this. If I need a long exposure or a steady shot I'll lock it to the tripod. I can put a 50mm f1.4 planar on my A7R, set shutter to 1/50th sec and set auto iso bracketing to 200-3200 and take pictures in low light that are better than anything I could have taken with a Contax RTS, fast film and the same lens. I could also walk into a studio and photograph a Ferrari with the A7R and the images would be good enough to be compared to the same images taken on all but the best medium format systems. M4/3 is to me like a toy when it comes to still photography. As an all out photographers camera I personally cannot see how anyone can look at m4/3.
Massimo Fanucci got a reaction from MiL0 in Sony A7S specs announced - S for sensitivity. 4K via HDMI to "third party recorder"