- The yom-tov tag wiki excerpt: "The Hebrew phrase for "holiday". Used for religious holidays such as Rosh Hashana, Purim, etc..."
- The chagim-holidays tag wiki excerpt: "the three pilgrimage festivals: Sukkot, Pesach, Shavu'ot."
That distinction sounds good to me. So does:
- Use yom-tov for questions about holidays on which activity is restricted.
- Use chagim-holidays for any Jewish-holiday question (except those for which a finer tag exists).
- Merge one of the tags into the other, and make the latter about all Jewish holidays (except those for which a finer tag exists).
The current state of affairs, though, is:
- Use either tag for anything.
Please state and upvote/downvote your preference among these and any others ideas you may think of.
(Don't bother upvoting/downvoting this question, as there are several conflicting suggestions in it and no one will know which one you like/dislike.)
Update: Per the votes, I've accepted Isaac Moses's answer. I've edited the tag wikis and excerpts and retagged existing questions accordingly.