The f/2.8 version is a macro lens with 10 elements in 9 groups. The 105mm f/2.5 isn't a macro and uses 5 elements in either 3 or 4 groups. I can't see how those designs are similar.
I used the 105mm f/2.8 AI-s micro very briefly. No fault of the lens -- A shelving collapse destroyed my Vivitar 100mm macro. I bought the 105mm, my wife bought me a Tokina 90mm f/2.5 macro, and I quietly resold the 105mm.) For macro "stuff," where you are stopping down to obtain more depth of field, it performs quite well. But at or near wide open and at distance, the Zeiss is a far better lens.