I also terribly regret the retirement of 4.1. From my own personal usage, for code or normal tasks, I clearly noticed a huge gap in degraded performance between 4.1 and 5.1/5.2.

4.1 was the best so far. With straight to the point answers, and most of the time correct. Especially for code related questions. 5.1/5.2 on their side would a lot more easily hallucinate stupid responses or stupid code snippet totally not what was expected.