I have owned the 105/2.5 first version and the 85/1.8 first version.
I kept the 105/2.5 Ai-S and the 85/2 Ai-S eventually, because I could not see any significant differences with the above mentioned, and the Ai-S lenses are more compact and lighter.
I like them both as much but tend to carry the 85 most (really compact).
I may not have had a good copy of the 85/1.8, or I may have an exceptionally good one of the 85/2, because most people on the Internet rave about the first one and say the latter is inferior. But my own experiment didn't confirm this.
The 105/2.5 Ai-S has an exceptional ability to display details in deep shadows while the 85/2 Ai-S doesn't (it may have a more "flat" rendition). This is where the subtle differences between the two lenses might be. Apart from that, they are both superlative lenses.
As for the differences between the 105/2.5 Ai-S and the 105/2.5 first version (Sonnar type) I'd say that they are on par as for sharpness on the focus plane, but the Ai-S lens has a more pleasant bokeh (less spherical aberration, so the OOF areas behind the subject are less "swirly" and more "creamy").
I know that there are people out there now adoring back those pesky spherical aberrations lenses designers have been fighting against for decades, so I won't comment any further... 😉