I have a Claude $200 (Ultra these days) plan and use Opus 5.5 for work with ultracode workflows and all the rest every day. I also use DeepSeek V4.1 Flash 1107 through a separate subscription plan with Pi.

Using DeepSeek I've made the Wayland compositor I use every day. It's finished now in the sense that it doesn't crash or have any bugs, nor can I think of any features to add or anything to change.

When somebody else is paying, I'll absolutely just throw Opus 5.5 at it. Who cares. It gives the best chances that the output is what I want, at no extra cost to me. But for my personal projects, using DeepSeek in Pi with a workflow extension is competent.

Sorry for throwing lots of text at you. All of this to say there's more to it than just which model is more intelligent. There's also speed, cost, and "good enough". Perhaps the problems I'm working on right now are just not complicated enough for "Opus is better" to be a real selling point.