Power off. I never used hibernation nor suspend (even on Windows) and as I don't use some of my computers for weeks, it just doesn't make sense to keep them suspended for so long. And now that I'm on Fedora Atomic Desktop with auto-updates, I would have to reboot regularly anyway in order to apply updates.
Only exception is the Steam Deck for which I kept suspend so I can pick up my games where I left off.

Oh right, I confuse the two