I suspect there needs to be a clarification about what things are what. I see Drupal and Joomla as content management systems, that is they play specific roles for some things. Moodle is a Learning Management System, that is something different. Moodle can be used inside the Drupal or Joomla shell, so they are not competitive, but rather, complementary, as Marcus has suggested. They are two different things. We need to not get too carried away with these terms, LMS v CMS, they are different tools for different segments of the market. One thing I have thought of is to use a Drupal or Joomla shell, and inside you have a range of PHP applications, Moodle, MediaWiki, Mahara, WordPress, and a decent diary tool, which Mahara may or may not be useful for and an email tool. The shell provides some security but more importantly, provides a single login device. Whatever tool you want to use, the shell provides the login so you actually do not have to log in to each tool separately. I have no idea how to make this work, of course, but there are some smart people out there who could do it.
Of course, if you really wanted to get serious, you could, as these are all Open Source, integrate them into a single tool, add in a Student Management System, and you would be developing a hugely powerful tool that you could maintain yourself irrespective of anything that might happen to the products you are using. As long as the web shell, Apache, PHP and MySQL, remains intact, without consideration to versions, then you could have a system that will last for as long as you want to support and the hardware does not outgrow it. That could be decades and in this world, that would be a phenomenal achievement.