> With LLMs I think this upside is much smaller now though.

With LLMs Tailwind wins. Because it's a very restricted set of classes. With regular "separation of concerns" CSS, LLMs will happily just pile on more and more and more CSS because they can't really analyze the code that's already there, and will miss and re-create huge chunks of CSS. Or write increasingly hyper-specific CSS to fix reported issues.

Anecdotally: in a side project I now have 10k lines of "pure" CSS generated by LLMs on top of Tailwind. The web part of the app is ~20k lines (not all of them are rendering anything on screen). No idea how to fix it :)