>>3554176The Df's build quality is great, it's build in the same factory as the F6, D5 and Z7.
It's also a much newer camera, being based on the D4 while the D700 was based on the D3S (itself replaced by the D3S before the D4).
What's the price difference where you live?
One thing to keep in mind since you will be using manual lenses is that you should consider ordering a focusing screen from
www.focusingscreen.com as, like most DSLRs, the standard ones (from either the D700 or Df) are not very well suited to manual focus.
Here's an example:
http://www.jerkwithacamera.com/nikon-df-split-screen-manual-focusing-screen/ 