I can't see why everyone is so bothered about noise, photography is about light if there is not enough don't take the shot, low light capability is only needed for concerts,sport, news my 5D has served me well and will do for more years to come even though i have gone back to film with 2 Leicas neither has AF and 99% of shots are in focus
Or, you know... anybody who wishes to photograph anything in the world during the entire half of the day when it happens to be in darkness. A little thing I like to call night time.
a better camera will not make you a better photographer
This is just false. I have been teaching my girlfriend basic photography over the last few weeks, and once she learned basic composition and exposure triangle and such, her decent quality photo rate is almost twice as high already with my 6D versus my Rebel T2i.
After like 3 weeks.
Now, granted, she has lupus which makes her very sensitive to the sun, so we mainly photograph at night, where the full frame excels. But that's ALL it took to already make a 3 week old photographer run up against a major limitation of an entry level DSLR and already begin to miss decent shots due to insufficient speed and low light performance.
Note that I also gave her my 50mm 1.8 to use, knowing that the older camera would not be as good in low light, while I was using the 24-105mm f/4L. Even with a 2.3 stop slower lens, she is
still missing more shots on the lower end camera than on the nicer one.
As soon as anybody gets the slightest bit good enough to hit any walls with the limitations of their cameras, a better camera WILL make them a better photographer by removing that bottleneck for them.
As for the topic of the OP, I think that calling the D600 just embarassingly flat out better than the 6D is simply incorrect.
For one thing, go look at the reviews on Amazon for one versus the other, bodies only.
The D600 gets 3.8 out of 5 stars, and the 6D gets 4.7 out of 5 stars. Over hundreds and hundreds of reviewers each.
Why? Well go read them, but short story:
1) Nikon's inferior ergonomics matter just as much as any technical optics or sensor differences do, and they are significantly inferior by almost all accounts of people comparing the two directly. Even the OP acknowledges this during his rant against the 6D.
2) The D600 apparently has a mirror that flings bits of oil onto the sensor... I don't know if this has been fixed, but that is a horrible Horrible HORRIBLE flaw, and it deserves every single 1 star review it gets for people afflicted by it. Straight up OIL. probably the hardest thing to get off your sensor at all, short of like... tar.
3) The 6D is a good solid full stop better in ISO noise performance
If not for the oil issue, it looks like they would both get fairly identical reviews, with the poorer Nikon ergonomics and ISO balanced fairly well by Canon's somewhat lesser other technical specifications.