[davidmanze]

I have a hard time to find obvious differences. This gallery I mostly set up for sake of bokeh: https://sojujo.smugmug.com/Testshots/2-different-85-mm-on-Z-7/n-sBzfZt

Please note that I was rather sloppy in terms of "scientific comparison": no tripod, two different bodies with the same sensor size, two different AF systems with some "impossible" subjects for each of them (that was also interesting to me). It's mainly to compare bokeh.

   I'll go along with the Sigma producing a nicer bokeh than the Nikkor there JoJu ..... but they had to choose one of the most difficult backgrounds to expose it ........ stones, gravel and general random clutter at distances which trip up many a lens.
     The Nikkor does what is the start of bubble bokeh, with that vague circular thing starting to form.

   If I was seriously doing portraiture I would choose Sigma ...... both the 85mm and the 105mm ...... but on a ML body.

  Nevertheless, the Nikkor is a huge upgrade from the AF85mm F1.8G .... and not unsurprisingly AF85mm F1.8D.

    Just looking on line this minute the Sigma Art is available for 805 euros on promo .....

"They"? If you're referring to the gallery I just put in the link to, it was my insignificant contribution to the gazillions of comparison galleries   for which I take full responsibility (and ownership, harhar). The concrete wall had loads of tiny details in a horrible, yet random frequency.

And as said, I really find it hard to look at a shot and say "aah, of course, Sigma Art..." as I don't do comparisons when doing portraiture.

If you're tempted by the Sigma, be aware: I had two copies as a rental, none of them was spot on with AF. Then Sigma published a firmware udpate, so I didn't had to use AFMA in lens AND in body to get the correct focus. The focus drive in the lens is really powerful, as I feel and hear in few moments when it was too fast to stop at the right point and races towards minimum or maximum. I would not recommend it very strongly to use it on Nikon's ML as in my eyes the genuine Z lens offers a very close bokeh at roughly 50 % of weight and much smaller size.

If one can live with a longer FL, the 135/1.8 Art has a shorter MFD, so you actually can do a bit of close-up work. The focus drive operates a bit smoother and the keeper rate is rather good.

    ........ the thought of buying both Sigmas and the Z7 is purely a pipe dream !!