What kind of clan site you are looking for.
My experience with different CMS:
1. Joomla:
Plus: Very nice design. Lot of extensions that take care of most of the needs. Very vibrant community. Very popular.
Minus: Little cumbersome to maintain. Difficult to move on to different host. Do not have multisite option except using paid extension.
2. Drupal:
Plus: Great for big sites. Multisite option so you install once but have multiple site. Maintain these from one place but still have different template and additional plugins for specific one only
Minus: Not that great templates available. Off late has become less vibrant
3. Wordpress:
Yea you will jump on me that Wordpress is blogging software and not CMS. But off late it is fast growing in CMS.
Plus: Very easy to install and maintain. Great themes and log of plugin available
Minus: After all it is not full fledged CMS
