No it's not. It means Defocus Control wherein you can control the blur of the subjects. I would go with the 135 f2, but wouldn't that be a little too far? Why not 105mm f2 DC or 105mm 2.8 Micro VR?The DC is a cropped sensor lens, so I would avoid that with the D600.
Are you saying those are your only options? If so, get the 150mm if it's the "f2.8 AF APO EX DG HSM Macro" version. If it's not, save your money and just shoot with the 85mm 1.4.