I'm not really sure such a 'silly' video proves anything. The video didn't cover areas such as dynamic range but if you want to look at the DXO figures the Nikon D800 doesn't demolish the 5D in all areas and whilst DXO figures are far from the be all and end all they should be given far more credibility than that video.
The colour depth figures are as near as dammit for both cameras, the iso whilst higher on the Nikon only equates to half a stop in real world terms and both cameras have a great low light performance. You could easily argue that the canon should be better given it has 50% less pixel density but as said they both offer 'stunning' low light performance. The film clip above shows the canons 'video' low light capabilities to be far better and given the 5d seems to be more focused on video than stills this is obviously where the canons engineers spent there time.
The only area where the Nikon does demolish the 5D is dynamic range. The canon loses 3 stops to the Nikon putting it in micro four thirds territory, not even aps-c territory. Its likely that the new entry level Nikon D3200 will get a higher 'overall' score than the canon 5D mark3 and I suspect thats whats causing canon fans the sleepless nights.
At the end of the day canon have made a very accomplished video camera and compromises would have had to have been made on some aspects of sensor design affecting still images. 6 of one and half a dozen of the other imo.