Frontend Backend Admin Login Password LOGIN● Template System ● Manage Content● Displays Content ● Install Extensions Drupal supports multisites installation out of the box. Wordpress from 3.0+ (or with MU). Joomla must extend.
References  Open Source CMS Market Share Report 2010  Open CMS Awards  W3 Techs  The CMS Showdown Idealware - Comparing Open Source Content Management Systems Survey Analysis Part 1: Developers and Documentation Wordpress vs Joomla vs Drupal Joomla and Drupal - Which One is Right for You? Version 2 What everybody ought to know about Joomla Why running the White House Web site on Drupal is a political disaster waiting to happen