Which is better? First an overview of both web applications.
WordPress
WordPress is blog publishing platform and a content management system. Have many features including user registration with simple permissions, blog posts, static pages, RSS feeds, cross blog communication tools (pingbacks and trackbacks), comments, extension system (plugins), template system and many others.
Drupal
Drupal is content management system. Shares many features and hosting requirements with WordPress including the above mentioned, but more powerful user system (permissions), ability to create your own content types and better (more complex) administration panel.
So which is better?
This depends on what your web site will be about. Both are very good applications and are very popular, with lots of extensions and themes. If you are starting a personal site/blog than wordpress would be the choice because it is easy to manage and have good and simple admin panel. Although drupal can be used for personal websites, drupal tends more to be community driven, and is better for large corporate websites. So the choice is yours, whichever you choose you won’t regret.