Wedding photography

Given the two I'd go with the D800. I don't think the Canon is worth the extra $500 that could go towards new lenses. From what I have seen, shot by a friend who owns an 800, it shoots incredibly at high ISO with very low noise. The D800 also has better color and image quality for stills which I know is very important for wedding photography.

The 5DMKIII handles iso noise better than anything I've seen. Canon L glass is legendary, 85 f1.2 and 50 f1.2 are probably the best lenses in their class. NIkon bodies have great ergonomics and fast AF systems and beautiful color. The 5D MkIII seems to be the industry standard for wedding photography. The tipping point is the video quality that Canon favors. I say I'd go with Canon.

The comparison I've seen shows them even in low-light.  This site claims that the D800 is better at high ISO, low light.  The fact that it doesn't go to as high an ISO in the settings doesn't mean that it does it with less quality.

It really depends on your needs though.  The Nikon iTTL flash system is far superior to Canon's.  The video in the Canon is going to be better.  The Nikon can uses lenses from the 1960s and has more options for add-on features like wireless transmitter, etc. 

Both are perfectly adequate.  I regard my D700 is good enough and both of these are far better, so your choice should probably be made for other reasons (like lens availability, etc).

i recommend nikon considering the price - quality of images is not much different - extra mpx grant extra cropping power and more edtails

I suggest nikon d800 set with nikkor 85mm f/1.4 and also wide lens nikkor 50mm f/1.4.

For tele use nikkor 24-70mm f2.8 which can get better pictures.

Those combination can get portrait, wide and tele foto.

Photography is an art, painting with light,,,,,,, machine(camera) secondary

I am Nikon user and I belive nikon is the better Dslr