Below, mouse over the various graphs to see his computed dynamic range for the Fujifilm GFX100 across the ISO range and with electronic first curtain shutter (EFCS, best choice for most stuff) versus electronic shutter (ES).
In summary and speaking only of dynamic range, there is no meaningful difference between 14 bit and 16 bit capture, whether with EFCS or ES. Possibly there are other benefits, as yet unclear.
See also Jim Kasson’s discussion of Fujifilm GFX100 dynamic range. In particular he states:
The presence of the Aptina-DRPix technology is evident: that’s what causes the jump at the transition from ISO 400 to ISO 500. All four raw channels have th same DR until the ISO gets quite high, at which point the green channels do a little better than the red and the blue. There’s a funny kink in the curve at the transition to ISO 200
EDR = Engineering Dynamic Range: there are several definitions, but the one I’m using is full scale over read noise, unnormalized for resolution.