I post some example images to say a bit towards my opinion on Nikons 105mm lenses
DSC_0669-Edit by
b j, on Flickr
DSC_9572 by
b j, on Flickr
DSC_1598-Bearbeitet-2 by
b j, on Flickr
All 3 of the above were taken using the oldest optical design. The 5 element in 3 groups Nikkor-P
The picture below was taken using the newer 5 element in 4 groups design
DSC_2052-Edit-2 by
b j, on Flickr
Differences between the Gauss and Sonnar design 105mm f2,5 Nikkors exist. They can be exposed when making comparison shots. I once did that, because I owned lenses in both designs.
In total I owned 4 different 105mm f2,5 Nikkor lenses. The Sonnar 105mm f2,5 Nikor-P (with 6 blade diaphragm. The very first design used 9 blade diaphragms), the Gauss 105mm f2,5 Nikkor-P.C with multicoated front element, the 105mm f2,5 Ai and the 105mm f2,5 Ai-S
The difference between the Gauss design lenses really is minimal. Sample variation wil most likely cause more difference then the modernisation of coatings on these.
With all but the Ai-S I used reversible snap on hood (HS-7) from the Noct Nikkor and 105 f2,8 micro Nikkor. It is a bit wider then the HS-4, which I find pleasant because it's less likely to bump into the lens when reverse mounting the hood. The HS-7 is also easier to find.
As to the rendering, the Gauss lenses are a it sharper towards the edges, but in the end I sold all but the Sonnar lens, because I prefer the transition from in-focus to out-of-focus elements. Again, the differences are very very minimal, but with OoF subjects at the distances I tend to place them in my photos, the older lens seems to transition a little smoother.
My version of the lens came with Nikons Ai conversion kit so it works perfectly on most Nikon cameras. The older lens is also slightly smaller and lighter then later versions, except maybe the Ai-S.
In the end, if you are looking to buy a 105mm f2,5, you can buy any version really, and verify you find a good copy. The pre-Ai-S lenses have a longer focus throw, which helps finding your focus. The Ai-S therefor is nice with it's short focus throw when taking snapshots, because you hardly ever have to regrip the focus ring when focusing from MFD to infinity.