Compare WordPress vs. Concrete5
WordPress is not a very modern PHP CMS and does not use Symfony or other components. It is very popular and earns it's position in the listing of Symfony CMSes.
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