Early on, iCloud Backup was inferior to an iTunes backup. That hasn't been the case for some time now, so I rely entirely on iCloud Backup. I pay the $0.99/mo to have enough space for backing up 5 devices.
In them you will see that I documented numerous SILENT failures of iCloud backups on ALL three of our iOS devices. I even furnished Apple with the Apple Configurator 2 logs of these failures -- at their request.
FWIW after my detailed evaluation of iCloud backups, I quit backing up our iOS devices via iCloud — iCloud backups were (perhaps still are?) not reliable enough to depend on even as a 2nd backup.
—GetRealBro
p.s. Yes I know we now have a new iOS. But have any of you actually checked to see if your “nightly” iCloud backups are working?