Screencap from D600 review
To me I rank in terms of the following factors. I'm not sure if its just a personal bias coz i'm a Xpro user but please let me know if you guys think differently.
Noise: D800 > MK3 > Xpro1 > D600
Sharpness: Xpro1 > D800 > Mk3 > D600
Grain / color / natural etc: Xpro1 > Mk3 > D800 > D600