Compare Reservoir vs. Joomla!
Reservoir is a Drupal 8 distribution focused on decoupled content management. It is developed by Acquia, the company providing enterprise grade Drupal hosting and solutions.
Joomla! is one of the big three PHP CMSes. Currently it uses only a single component from the Symfony project. Joomla remains a strong contender with a large number of users and extensions.
CMSes vailable for comparison: BackBee, Bolt CMS, Concrete5, Contenta, Contentful, Cosmic.js, Craft CMS, Drupal 8, eZ Platform, Fork CMS, GraphCMS, Grav, Jarves, Joomla!, Kunstmaan, October CMS, Open Orchestra, Pagekit, Pimcore, PyroCMS 3, Reservoir, Spress, Sulu CMS, Symfony CMF, Symphony CMS