Nikon D600 vs. Canon 6D in Low Light?

Not exactly. I would buy a Canon 6D + 24-70 f2.8 MK II now instead of my D600. Roughly the same price as my Nikon D600 + Nikkor 24-70 f2.8 combo.

I do not like the compromises of the 6D vs. the 5D Mk III. If they had come out at the same time, I would go for the 5D Mk III. However, the 5D Mk III is a year old tech. Technically technologically obsolete :). Yes, I know i'm exaggerating. But the point remains. I don't like buying a one year old model when refreshers come out every two years... So, my solution is to get the D6 now and that superb 24-70 Mk II lens, and change the body to the 5D Mk IV when that is out by say Christmas 2014. I think that's a reasonable approach.

And yes, if there was an image stabilized version of either 24-70 f2.8 lens with nice bokeh (The Tamron's bokeh is not great) i would buy that...

I'm all about low light / party and fashion show photography and portraits (of hot models.) That's 95% of my shooting. (Hot) ladies walking down the catwalk sometimes in fairly poor light.That requires continuous subject tracking AF and shutters speeds of 1/250. Low light performance is critical. So is a good AF system.

Now you probably understand my dilemma.