Summary

Those functions are quite similar. In #30956, I tried to relate them via

a.update(props) is equivalent to a.set(**props)

And got the the question, why we have them both.

From a quick look at the code, it seems set is doing name normalization, so I wrote

        This is a slightly more efficient variant of `.Artist.set`. It's
        primarily intended to be used internally and by third party
        plotting libraries. End users are recommended to use the more
        readable and flexible `.Artist.set`.

        ``a.update(props)`` is equivalent to ``a.set(**props)``, but does
        not support aliases / shortcuts; e.g. you can do ``set(lw=1)`` as
        a shortcut for ``set_linewidth(1)``, but you cannot do
        ``update({"lw": 1})``.

But turns out that is not true either. While update does not normalize, it likely will just call set_lw().

This needs more investigation.

Proposed fix

Identify whether there are any behavior differences or whether it's just the API (props vs. **props).

This possibly involves digging into the history.

Document the findings and define the scope when/whether update should still be used.