Tangential question: For the rare public-long-lived-topic-branch why merge over rebase?

For unpublished branches, I feel like I generally have a harder time managing conflicts when repeatedly rebasing a long-lived topic branch versus repeatedly merging it, and I think rebasing takes longer? Maybe that's a figment of my imagination since I rarely ever do this. Concretely, in this case, git merge is clean but git rebase fails once (although it fails when rebasing a now-obsolete merge which has become empty).

For published branches like this one, I don't want to rewrite published commits / perform non-fastforward pushes to published branches.