Best way to upgrade ubuntu 18 - upgrade vs clean install

Hi Guys,

I have a vps since 2015 that's currently on Ubuntu 18. I'm planning to upgrade to a more recent version.

The main thing I want is to avoid downtimes. Also don't want to be stuck troubleshooting and fixing an upgrade. If I'm tired of it I want to be able to leave it and come back the next day. What's the best way to achieve this?

Upgrade:
If upgrading I was thinking to save a snapshot, import it on a blank vps, do the upgrade and make it all work and then import the snapshot back into the main vps.

Clean install:
Clean install on a blank vps, snapshot and recover it on my current vps.

What do you think?

Thanks in advance for your help,