Most discussions like this start with the fact that an in-place upgrade is far easier but riskier if anything goes wrong. Side-by-side is more work and you run the risk of forgetting something. But if something goes wrong you just move back to the old instance.
I thought about something that isn’t usually part of the discussion this week while working on a side-by-side migration.
Read on for Kenneth’s insight. My general preference is side-by-side updates on a new server, as that helps get rid of operating system bit rot as well.