I agree with Salathe, depends on what you are doing. Simple blogging you can't go wrong with Wordpress. Joomla is good if you are going for a more full featured site, but even then, alot of the features will go unused by most people. It's important to find out what your needs are and then go looking for a package that meets your needs.

Anyways, I prefer Drupal to Joomla anyways