Compare Reservoir vs. Kunstmaan
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.
Kunstmaan Agency has created a number of Symfony2 Framework Bundles to enable developers to create web applications with CMS features. It's not a complete product in itself, but offers flexibility for skilled developers to create easy to use site experiences for content creators.
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