In WordPress, the little programs that add features are called: plugins
Pros: If you think WordPress is only for blogs, your definition needs an upgrade. WordPress can handle multiple authors, specialized content types, and pretty much anything a user would expect from a CMS. WordPress is legendary for being easy to learn and use. It's also got a sweet user interface. If your needs are straightforward, WordPress could easily be the best choice.
Cons: If you're planning to customize your site heavily, Drupal is probably a better choice. WordPress developers may disagree with me, and with over 15,000 WordPress plugins, they could be right. But the core WordPress program needs to be updated fairly frequently. These core updates can often break your existing plugins, and thus your site. In Drupal, on the other hand, it's a major priority that core updates shouldn't break anything. Drupal is designed to be extended with tons of modules.
Of course, if you pick the right plugins, your WordPress site may update just fine. It's just an issue to keep in mind.