Compare WordPress vs. Grav
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.
Grav is a fresh flat-file database which is easy to install. It uses a number of Symfony components and is very fast to get started with.
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