CMS code base comparison
Drupal
Joomla!
Wordpress
Plone
(These graphs depict statistics for the core of each project, and do not include contributed modules, extensions or third-party plugins.)
Conclusions
- All projects have been growing in size. No exceptions.
- Drupal has, by far, the smallest code base. It's lean and mean. Joomla!'s code base is about 8 times bigger than Drupal's. Even Wordpress's code base is larger than Drupal's.
- Of all tools, the WordPress code has the fewest code comments. Drupal and Joomla!, on the other hand, have the best documented code.
— Dries Buytaert