@b0rk I used both in different situations, so the idea that it's situational appeals to me personally. I think I look at it as: how likely am I to care about my changes to upstream as a logical series? If I want to revert some of my changes, bisect compared to the upstream, port some changes to other projects with the same upstream, or send a subset of them upstream, rebasing now will save me time later. If not, I probably don't care and will merge.
@b0rk Proton and Wine Staging are both examples of long-lived forks that I think rebase specifically because they want very detailed bookkeeping on the current differences from upstream, but not necessarily how they got there.