It is always best policy in my opinion, to upgrade to the next OS version after the first (point) release. Each new version of the OS (eg, Win 10 over 8.1) has additional security measures not in the previous version. I use Mac primarily and I always do fresh install at the .1 update (eg, 10.12.1 and not 10.12). I run Win 10 on my Parallels VM.