Drupal is a great CMS, it is just behind Wordpress in number of users and much easier to use than Joomla. Drupal needs more more of a learning curve than Joomla, but offers more functionality for sophisticated websites. I had experience with both drupal and joomla cms, they r both good, drupal is more flexible cms. Joomla – a very popular open-source CMS that is found at the heart of many well known websites (the United Nations is just one example). Joomla looks more popular than Drupal, probably because of high number of newbie users higher Google-
PR, better Alexa rang, better placement on Google-Trends and Twitter.