Compare Contentful vs. Concrete5
Contentful is a pure CaaS (Content as a Service) player. It comes from Berlin, and is currently the global market leader for decoupled hosted content management.
Concrete 5 is a long running content management system. It is known for it's user friendly interface and with it's recent iterations has moved to adopt Symfony components.
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