At learningdslrvideo they have a nice, 18 min video that reviews both cameras one against the other.The comparison is done from a film-makers perspective, but all aspects are taken in account. The EOS 5D Mark III stands out for its great high ISO performance and its all-round capabilities. From the conclusion:
So in conclusion on the Canon side, having the aliasing issue fixed is nice and the low light performance is insane, I am really enjoying the headphone jack, but I wished they gave us 1080 at 60fps, and a tilt out screen. For the Nikon I really like the amount of latitude I get from their neutral picture style, but I’m not crazy about the high ISO performance or the white balance issues.
At the end, which camera is the reviewer going to grab? The EOS 5D Mark III:
After I had finished all my testing and I was heading out the other day […], I grabbed the Canon instead of the Nikon, the main reason I grab it was the low light performance where I was headed, my style of shooting is mostly using available light, so for me I am going to buy the 5D3 since I can push ISO’s without worrying, and also I don’t have to worry deleting shots with nasty aliasing.
Next three videos cover particular aspects and settings.
Check the latest 5D Mark III pictures uploaded to Flickr clicking here.
World-wide 5D Mark III availability and price check:
America: B&H Photo, Adorama, Amazon USA, Amazon CA, KEH Camera, BestBuy, Canon CA, Canon USA
Europe & UK: Amazon DE, Amazon UK, Amazon FR, Amazon IT, Wex Photo Video, Park Cameras, Canon DE, Canon UK, Canon IT, Canon FR