Cost-adjusted,it might be ahead.

It's key to name the boundary conditions. Unlimited cost is a very HN assumption.

Really depends on your use case.

You are right that there's plenty of use cases where Opus 5.5 is better.

True, it isn't neck-and-neck. It's neck and balls. Deepseek's balls and Opus 5.5's neck. Whatever you can build with Opus 5.5, I can build in the same time, 1/500th the price with Deepseek Flash 4.1.