Drupal has a superior architecture and very SEO friendly. It can cater to your needs, it can be used for a simple FAQ site or a very large million visitor site.
Here are some Key pros and cons of the two systems.
Drupal
* Rock solid & high quality platform
* Real multi-site-feature (only one installation for several sites)
* Any Kind of user groups & user permissions, OpenId compliant in Version 6
* Can run membership and community sites, not only CMS etc
* Powerful templating system. Any XHTML or CSS template can be easily converted to Drupal.
* Drupal needs a little time investment to realize all the huge possibilities of Drupal
* Clear, high quality code and API (easy to integrate with other solutions etc)
* Flexibility and no known limitations
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Many high profile sites use Drupal (e.g.: MTV UK, BBC, the Onion, Nasa, Greenpeace UK, New york observer. )
Joomla
* If you are not techy its good to start
* Easy install & setup with your mouse
* Easy learning curve
* Cannot integrate other scripts etc. to your site
* Generally you cannot create high-end sites, without investing huge amount
* No SEO out of the box, URLs are not search engine friendly.
* Server resources utilization is more compared to drupal
* Only one site per installation
* No Single Log-in to several sites
* No User groups & permissions
* More intuitive administration user interface
* Some polished modules for things like calendars, polls, etc.
* Modules cost you money
Having said that is true, you can have all those feature in Drupal, but then it will take you quite a while to get there and you will see your site's speed slowing down. Drupal is awful when regarding speed.
Drupal has so many features and you can do website with Drupal. But it is not user friendly, and I am afraid to say that the administration is crap and the technology is outdated.
Drupal used to be the best for years. As a result this attracted a lot of developers to it, creating a huge community. Obviously such a big community does a lot of noise claiming that Drupal is the 'best CMS'.
You can read all over the Web how perfect Drupal is. But the wold change every day, and the Internet too. What was excellent 5 years ago is more than outdated today. New CMS have been developped integrating the best of today's web technology. Drupal simply cannot compare with them.
People are talking about the next Joomla 1.6. Any thought about this?