6D + Canon 50/1.8 or D600 + Nikon 50/1.8? Help me decide.

Both are fine cameras And extremely capable compared to just a few years ago. Both are capable of stunning results. Real differences are actually pretty small and often boil down to personal  preferences. The choice may have much to do with the type of subject you normally shoot and the lighting conditions you most find your self in. The Canon has an advantage in Low light situations, while, as you point out, the Nikon has a slight advantage in DR range. Those kinds of advantages mean different things to a person who predominately shoots landscapes in extremes of DR vs the the stage photographer who works predominately in low light. What type of photographer are you?

The folks here are often passionate about there chosen equipment. I know you have also been researching extensively and are honest in your query. Hopefully folks will take that into consideration and be able to give honest unbiased opinion and example in as civil a manner as possible. Good Luck.  What ever you choose...I suspect either system will be up to the task, easily.

Good luck in your quest.

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My opinions are my own and not those of DPR or its administration. They carry no 'special' value (except to me and Lacie of course)