If you are primarily concerned with AF accuracy, a lens with an electronic connection to the camera and an internal SWM will very likely provide more shot-to-shot consistency than a lens focused by a mechanical connection from the camera (assuming the body, such as your D750, is from the last five years or so). Mechanical connections are much more subject to variability based on environmental factors (primarily temperature) and mechanical wear over time. Electronic lenses tend to have position sensors that report the actual lens position back to the camera, thus adjusting for any environmental and wear factors. Older bodies don't always have the ability to take advantage of the information from the more precise focus position sensors in newer lenses, but most Canon and Nikon mid-grade and up bodies from within the last half decade or so generally do.
In either case, the ability to calibrate a camera body and lens to each other is paramount. We're well beyond the point where our ability to see differences based on small variations from one unit to the next has exceeded the practical limits of manufacturing precision and tolerances. This was not so much the case in the film era when the variations in the flatness of the film itself introduced more variability into the equation than is the case with sensors that are very near perfectly flat on a microscopic level.
MTF data published by manufacturers is theoretical based on a perfectly blueprinted lens. No such lens actually exists. Often the differences from one copy to the next of a particular model lens are greater than the differences between the average measured MTF performance of 10 copies of lens "A" versus ten copies of lens "B".
In general the consensus from most reviews is that the 85mm f/1.8D is almost as sharp as the 85mm f/1.8D in the center, but the "G" maintains sharpness to the edges and corners much better than the "D" dies.
For more regarding Nikon "D" versus "G" lenses in general. please see: Can I get the same results with Nikon D lenses as with G lenses?
For some in-depth reading and real world measurements you can look at the series Roger Cicala at lens rentals.com did back in the summer of 2015 regarding variability from one copy of a lens to the next. One of our own users, Brandon Dube, was an intern for Roger that summer and did many of the measurements Roger analyzed in the series. This entry covered short telephoto primes in the 85mm/100mm/135mm range. (The Nikon 85mm f/1.4 and f/1.8 lenses referenced are the "G" models released in 2010 and 2012, respectively). He also summed up the series on prime lenses up to that point at the end of the article. The first entry in the series provides a lot of background on the methodology and just what the information presented on the graphs means.
The gist of the entire series is that many newer lenses from the major manufacturers, including the Nikon 85mm f/1.8 G, are more consistent in their optical performance from copy-to-copy than the older designs created back in the film era. Of course razor sharp MTF isn't worth much if the AF doesn't work well unless you are carefully focusing manually. For more on that you can read Roger's classic blog entry here: Autofocus Reality Part 3B: Canon Cameras. A few weeks later he did a Nikon FF version with fewer data examples, but if you read all of the way to the bottom you can see that the results were very similar.