Here are 100% crops taken with both the Nikon D600 and Canon 6D using 135mm & 85mm portrait lenses @ f3.2
Hmm, Nikon looks crisper and cleaner to my eye between these two images
It's definitely sharper, but a tad less flattering too - just look at the tiny blonde hairs at the bridge of the nose and above the upper lip too, sort of reminiscent of initial criticisms of the D800
Different tastes, I guess. I prefer seeing those tiny hairs rather than the smudgy look of the Canon image because when doing macro work, I
want to see those tiny hairs on an insect. I can always smooth out skin in PP, but for when I want the detail it needs to be there first place since I can't manufacture it in PP. Actually the Canon images looks like a rather amateurish PP job like I used to do when first learning photoshop

Just my $.02