I've settled on "follow the existing/upstream project's style; if it's a new project, follow the language's idiomatic style". I personally (strongly) prefer spaces over tabs, but I've inherited/forked plenty of projects that use tabs in JavaScript for example, and I just set my editor and formatter to use tabs in that project.
I think the ideal situation is a language with an official or at least commonly accepted formatter, so that existing and new projects will essentially always follow the same style and you never have to think about it. Like "go fmt" always using tabs. I don't like tabs, but I like that kind of enforced consistency way more than I dislike tabs.
That's also why I like using opinionated third-party formatters like prettier and black. Combined with pre-commit hooks, you almost never have to think about style and can just focus on the code. Plus diffs are cleaner.
I used to feel very strongly about this. Then I started using Common Lisp and discovered the abomination that is tabstop. This archaic "feature" leads to tab width that varies across the line and seems to be hardcoded in every text editor out there. Worse, it's only useful if using tabs for alignment which is completely broken anyway! At some point I intend to patch the source for the editors I use to remove this nonsense.
Admittedly this is something of an edge case - how many languages other than Lisps involve alternating layers of indentation and alignment? The more common C like languages don't suffer from this at all.
At this point I'm largely convinced that more or less all of our tools, languages, and conventions are poorly thought out, brittle, and inelegant. /rant
I think the ideal situation is a language with an official or at least commonly accepted formatter, so that existing and new projects will essentially always follow the same style and you never have to think about it. Like "go fmt" always using tabs. I don't like tabs, but I like that kind of enforced consistency way more than I dislike tabs.
That's also why I like using opinionated third-party formatters like prettier and black. Combined with pre-commit hooks, you almost never have to think about style and can just focus on the code. Plus diffs are cleaner.