Of course it is just another opinion, but I own and use all 4. 28mm Ai-s , Ai, 2.0 and 3.5. The 2.8 Ai gets little love from others, but I get along fine with it. I love the long focus throw and at infinity it is to me the same as the ai-s. The Ai-s is better up close and the 3.5 is great stopped down a bit all over. That said the 2.0 is superior and the last one I would ever sell.