The people who switch back and forth between providers every month are a very small, but loud, minority.

OpenAI did pull ahead in limits and quality for a while. Anthropic took it back with the Opus 5.5 rollout. I maintain subscriptions to both providers and use both daily. I can confirm these differences were real, not "it's just vibes and nobody knows anything".

I would bet that 99% of each company's paying customers either did not notice, or did not care enough to consider changing.

> the only people I hear talking about actually switching away

Opus 5 had really bad writing so I switched to OpenAI, though Opus 5.5 largely addresses that and it's not like them building some Slack integrations (or any other non-core stuff) halts the actual model training in any capacity. For what it's worth, Astra is a pretty good model and for all I know the new Sol will be as well, it's just that it's getting more expensive.

They've definitely lost many experienced devs who can see Anthropic's offerings are insuperior to OpenAI/Codex; I know I am not the only one.

I think it's pretty subjective if you mean "lead" to be capability and not raw number of users. I jumped back and forth quite a bit last year because there were some pretty major shortcoming in both. Now they're both quite reliable without too much hand-holding. Codex now consistently works better for the kind of work I'm doing, and it's good enough that I'm not inclined to go to claude, because I don't have any significant problems.