Picture by arne.list from Flickr
A very useful focal lenght, maybe a bit on the long side on the DX format.
The 85 Ai performs very very good, but apart for the ugly plastic covered barrell of the AF sibling you don’t have a reason to buy the Ai model.
Only in two cases you could be interested in this version:
a) you own an FM2, an F3 or another classic manual focus camera, and you don’t like the look of the AF model (but it’s not the look that takes photos); or
b) you find one of this in pristine conditions and dirty cheap. Otherwise go for the AF.