In his Joomla Versus Drupal blog post (worth reading in its entirety), Joe Kemp, who has used both systems and built sites with them, says, "Drupal is more like a programming framework or language, while Joomla is like a program. Joomla is a good CMS if you are just starting out backend developing and your websites are not very ambitious. But after some time you will find it limiting and you will want something that is more general purpose."
However, Kemp notes, "Although I have put down Joomla, it's a good CMS to start with if you are new to the field. If you want to set up your own CMS with the least hassle and are not too worried about a custom architecture then Joomla is not a bad choice."
Making the choice
Justin Powell, who runs Twin Red Media, a small boutique agency that has standardized in Drupal, says, "We've used other CMSs as well, including WordPress and Joomla (and Joomla's predecessor, Mambo). While Joomla maintains an edge on ease of use, Drupal is much more flexible and scalable. We've deployed Drupal for sites where Joomla would work fine so the site would be 'future-proof' if the client later needed to deploy new functionality that Joomla couldn't easily support."
"We've been developing websites using Drupal (exclusively) for over five years," says Redfin Solutions' Wells. "We've built sites for corporations (PUMA North America), Universities (Harvard, UNH, Appalachian State), non-profits (New Hampshire Public Radio, the National Schools Public Relations Association, the Learning First Alliance), and many others in various sectors. "When we started years ago, we chose Drupal because at the time it was the most 'developer-friendly,'" says Wells. "We wanted the ability to build custom add-ons easily, tweak things we didn't think were quite right, and make sure we could extensively alter the look, feel, language -- everything! Today, Drupal is still this developer-friendly. I believe Drupal is still ahead of Joomla on the developer side of things."
"You often have a decision on CMS based on resources or business, not the technology," says Mitch Pirtle. "The good news is either way, you're picking a CMS that's more than worthy. Both are free, both have abundant 3rd party communities backing them up, both have a history of success."
And, Pirtle points out, "If neither Drupal nor Joomla seems a match for your situation, you've got lots more choices. For example, says Pirtle, "There's Plone, which is a CMS built on top of the ZOPE application server, which is a Python product with some C code; Radiant CMS from the RAILS community; SilverStripe; and Alfresco, a Java platform, which has a web services interface, and is aimed at the enterprise -- if you're a big publisher, you'd most likely go with Alfresco instead of Drupal or Joomla."