Drupal, emerging from discussion of BBS, grows up to an amazing CMS. Drupal 7 is more powerful:

• Easier to use: Fresh new management interface to facilitate your daily management work. More features for site builder and content editor
• More flexible: Define your own content structure; Add more self-defined fields for content, user and comment; More than 300 Drupal 7 specialized modules to build your site
• More extend-able: Improvement in JavaScript and CSS and Cache, etc to make your site stable and high performance
• Open source: Drupal community provides a lot of new/improved modules, themes and Drupal versions.