No contest, Nikon wins every time. ......
Well, to be perfectly honest, I don't think that is the case.
Here are some of the key features that in my opinion, swing it for Canon:
• Higher ISO
• Higher FPS
(for Nikon, you have to spend HUNDREDS MORE for a grip, switch down from FX to DX to get the same FPS! FAIL)
• Substantially better Expanded ISO
- although I will be honest, I would never shoot 50K-100K ISO unless I was desperate for the image, but hey, it is here as a feature!)
• More Points of Autofocus for Canon
These are some, not so key features (for me) where Canon is better:
• Continuous video time (Canon is longer)
• Battery Life (Canon is slightly longer)
Some KEY features Nikon has over Canon is the expected Shutter life of 200,000 cycles
• I take about 10K pictures a year and this translates into 4-5 years of more use!
• this one is excellent for Nikon.... USB3.0 .... this substantially decreases image/video transfer rates and this is a must today, I am surprised Canon fell asleep at the switch on this.
• Higher resolution (I will wait and see if this is that noticable)
• DX/FX for Nikon, Canon is only FX
• HDMI compressed output for Nikon, but this is a Camera to me not a camcorder, great feature, not important to me. Both have HDMI recording. Important to a press guy maybe who has to upload fast.
Canon also has Built-in HDR mode for 3 images. I like this. I have not read, or missed it, if the D800 has this feature.
I am a hard core Nikon fan, but you have to explain to me how NIKON wins here every time? In no way, do I consider the trade offs here a wash. For the features I think are important, I would say Canon has it for $500 more.
Would I change over for the slight difference.... NO.
Do I personally think that Nikon is the big spec winner here, the answer is NO as well. For the key features I like, Canon has the edge.
However, I will reserve total judgement until I can see images side by side, for both cameras, but I suspect that will be a wash.