When I ran OwnCloud (on Debian), I installed from their APT repo, and one "apt upgrade" handled everything. It was nice and easy, and I didn't have any problems with it.

NextCloud uses its own updater* (which I don't like), and aside from some recent MariaDB snafu it's been very low maintenance.

  (*)sudo -u www-data php /var/www/nextcloud/updater/updater.phar