There is no clear winner
At the level of these cameras, it is your skill as a photographer that determines the image quality, not the camera. A camera is a tool. The 5D and D800 are some of the best tools available, but you have to know how to use them. Put another way, you can buy a $20 hammer or a $200 hammer, but if you don't know how to build a house, the more expensive hammer won't make you a better carpenter.
The bottom line is if you want the best quality photos, you have to learn the craft of photography first.