Nikon D600: Are the "benefits" of this camera really worth it over the Canon 6D?

As i understood from one of your answer, your main concern is the low light situations and there the 6D is much better that the D600. the High Isos capabilities of the 6D are amazing and the sensitive of the center AF point -3EV is the best and will be able to focus almost in the complete dark, if you are not mainly shooting sports or action, then go for the canon 6d.