Is a clean install better than upgrading? has been reopened again. This will make it easier to keep it up to date. There's less incentive to keep a canonical question up to date if it's closed, and it's harder to review possible duplicate questions if the logical canonical "duplicate of..." question has answers which contain obsolete content or are not up to date.
The objection that it is opinion-based still stands, but it is inherently a toss-up because the answers to this question contain many facts too. In addition to the aforementioned macOS and Android users are provided with a clean, fast and error-free upgrade by default which gives their users the impression that upgrading is better for them than a non-defaultseries of not offered by default clean installinstallations. Ubuntu is more open source by designdesign than macOS and Android. The Ubuntu user is free to modify the operating system, so other installed apt packages are upgraded along with the core operating system packages when upgrading Ubuntu. Otherwise something might not work.
Ubuntu is open source by design has resulted in a more complicated upgrade than in macOS or Android, so we should leave this question open in order to pave the way for a smoother and more successful release upgrade for Ubuntu users. Repetitively closing this question and scattering the most up-to-date information about upgrading Ubuntu all over Ask Ubuntu cannot fully replace the benefits of having one canonical question.