One nice thing about snaps is that since they update themselves automatically, the snap developers/maintainers (who curate the snaps) know that whatever they send down the pipe will get installed automatically on a whole bunch of live instances. That places tremendous pressure on them to send something down the pipe that is stable. And it furthermore places a high incentive to be brutally honest about what is stable, and what is not. They vet a version as stable, by placing that version in the “stable” channel.
And by installing a snap, one places extreme trust in the snap developer/maintainers that nothing even slightly unstable will come automatically down the pipe (however, you do get the chance to roll back to the previous version, if you know snap well, and really, really read the man page of snap.)
Contemplate that before you decide to install Nextcloud from a snap. So far, my version 13 snap (stable) has been working great, BTW.