Specifically, 3.8 Flash suffers from far more hallucinations than 3.1 Pro and frequently ignores the context between consecutive messages. These two issues are fatal to the chat experience.
Because of this experience, I believe that benchmarks are quite limited to evaluate a model's real-world performance, and most current benchmarks focus on coding performance rather than chatting. At the moment, I have almost no reason to use 3.8 Flash.