seo – Which property should I use in Google SearchConsole

Registering the non-canonical properties allow you to check/diagnose configuration errors. For example, if a canonical redirect should fail (or be incorrectly implemented) for whatever reason or SSL cert renewal failures and/or pages aren’t being indexed on the canonical property, you have no way of knowing (without doing a site: search) whether those pages have been incorrectly indexed on a non-canonical property by mistake.

That’s 4 properties (not 6), the first two are the same as the second two.