Here on meta, we have separate spam and spam-handling tags. They are not even synonyms. A few questions are even tagged with both of them.
Since only seven questions in total are currently tagged spam, three of which are also tagged spam-handling, and spam-handling is the tag we've pretty much all been using lately, you might be wondering why I'm even asking this, rather than just retagging them all spam-handling.
The reason is that I'd like to make spam the main tag and spam-handling the synonym, for two reasons:
I've heard that's what other child metas use for this.* I guess a SEDE query could show this rigorously, but a quick look through the top sites' child metas seems to confirm it. The network-wide meta site also uses spam and not spam-handling.
There hasn't been a difference between spam and spam-handling. But someone may ask a question about the promotions policy, along the lines of "Would it be spam if I...?" There, the topic of spam applies, but the question is not really about spam-handling. I don't think we want the granularity of separate tags, and spam is the slightly broader one, so I think we should use that.
So long as we make one of the two tags a synonym of the other, I think the outcome is fine. But I think it would be best if we used spam as the main tag.
One benefit of making them synonyms instead of removing one of the tags from all the questions that have it is that we can avoid bumping a whole bunch of meta questions by editing (seven to detag spam, and far more to detag spam-handling). Bumping multiple meta questions has quite a visible effect since meta is slow, though it's not actually harmful to do so.
A more important benefit of making them synonyms is that either tag is likely to come back regardless of what gets decided here: spam-handling out of habit, and spam because it's the obvious choice.
* This post originally stated that the spam tag was one of the tags that new sites' child metas are created with, but that appears not to be the case.