Key pros and cons of Drupal vs Joomla

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
* 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

System Requirements:

* Drupal can work with MySQL and Postgres while Joomla is known to support only MySQL
* Drupal can work with Apache or IIS while Joomla is known to support only Apache
* Joomla support SSL logins and SSL pages. Drupal not known to support it.

Site Management

* Drupal has free add on for Workflow management. Joomla not known to have one.
* Drupal has inbuilt Translation manager. Joomla has a Free ad on for the same
* Drupal has more   granular priviledge managment

Interoperability:

* Drupal has iCal support [Add on] , Joomla not known to have one.
* Drupal is XHTML Complaint. Joomla not known to be one.
* Drupal has excellent versioning and Audit trail which Joomla lacks