I shoot mostly landscapes including sunsets and sunrises. I do some 800-1600 ISO work but not a ton. My biggest thing is that you can buy a 6d from canon refurbished for about $1,400. The only reason that is a consideration is due to having a newer sensor more so than features. I could care less for GPS or wifi.
5dc was great for its time and can still take amazing images.
However, given the choice, I'd get the 6D as its a more advanced camera all round and will last you years and years.