If You're Looking To Buy A D800 Or 5DMK3 Watch This Video
Dave Dugdale from Learning DSLR Video has put together a fantastic video comparison of the Nikon D800 and the Canon 5D MarkIII. It's a unique view as Dave is an amateur and not an endorsed pro, so the video is unbiased and stays true to the facts. But don't let him being an amateur throw you off, he is very thorough and I learned quite a bit of useful info about both bodies while watching this. Even at 20 minutes long it was a fairly easy watch, Enjoy!