Looking for an objective comparison between WordPress, Joomla & Drupel
One of our marketing associates, Karen wrote an article a few months back comparing these 3 CMS giants. The article can be found here. This should give you a good overview of the similarities and differences between them. If you have any further questions that the article failed to clarify on then i'll try my best to answer your question more directly.
We actually have a post about these 3 popular CRM. You can find it right here http://www.business-software.com/blog/comparing-the-big-three-cms/
For a quick summary:
Wordpress: super easy to use. A lot of things are pre-made for you already, you just have to play around to get a hang out it.
Joomla: Still super easy to use but a little harder than Wordpress
Drupal: More complex. Allows you to create whatever you want but you need to know coding for it.
Hope this helps!