>>4210820Nothing particularly, it handles low-ISO (under 800) better than the D5. The cool thing about the Df is its wider compatibility with vintage lenses. You can use pre-AI glass without mount conversion, as far as I know it's the only F mount digital that can.
But yeah, the D700 is incredible. If you want a cheap body to fuck around with, I highly recommend it. The price delta between it and a D850 is not that vast though, if it were me I'd try to get the last best DSLR ever made.