I'd say it depends how many different boxes of information you want on your front page.
Wordpress is pretty easy to set up, has plugins for different sources for your posts, but is basically just posts and pages.
Pligg is the same thing, right? One major flow of information.
Drupal and Joomla are more what I'd call CMS's. They have a lot of different plugins, including forums, voting, etc. These packages are a lot more flexible, but also a lot more complex to set up.