One thing that I really like from the Nikon D600 are two things (I am not sure for the rest but for me these are pretty important differences )
One is the possibility to turn the camera into CROP mode.. I think that is genius , I for example love the crop for my sport shooting, giving reach to more normal lens and effectively doubling the use and flexibility of the lens and body, I think that is pretty cool
Second: The pop up flash, I know everyone says that they will NEVEEeeeR!! use the pop up flash, but the truth is for me , that in many occasional parties and reunions I use the pop up flash as a life saver when I am not carrying my extra flash AND I use my Command flash quite often I must say for firing my flash Off Camera
I am sure that both 6D and D600 will be amazing cameras taking fantastic fotos, but I will confess that the Nikon offering looks very sexy to me
Is that enough to Jump Ship? not at this time, I have a few lens and for my application is working nicely
but I will be looking a the reviews and comparison of both cameras closely