From DPreviews (Gold Award) review of Fuji GFX-100:
"Our testing shows there to be less than a 0.1EV difference in DR between 16-bit and 14-bit mode, because the camera's pixels aren't producing a signal that warrants the additional encoding precision. So while there is, in principle, a <0.1EV difference between 14 and 16-bit modes, this will only exist at base ISO and will only come into play in tones already impacted by the PDAF striping. In short: we could not find any reason to use 16-bit mode."
DPreview is not the greatest review site out there, but in this case, I agree. The trade off is not worth it for me.
I bought the Fuji because it was the first fast, agile, PDAF, IBIS, Focus tracking, digital MF. To trade a lot of that away for a non existent bit depth difference, (theoretically better, but not in reality) is really not worth it for me. You may feel different, of course.