If you have several hours to compare what we consider the two leading Content Management Systems out there- this thread on the Drupal site has it all- but this short paragraph summed it up pretty well:

WordPress vs Drupal; what’s in a reputation? | drupal.org
And here is where I raise the usability/user experience issue.
Wordpress got it by the hand. Not only it validates out of the box, the experience for a non-tech user is great. It was actually FUN getting it to work. It wobbles when it comes to the categories (too simple but it works anyway for basic stuff), it doesn’t have half the functionality offers, but within its reduced scope, it is solid, and so very easy to use, to install, to understand.

Drupal, on the other hand, is a great, great tool, I appreciate the enormous effort from a lot of very bright and willing people and i’ll be damned before turning my back on it (not just because of the functionality, but because of the spirit behind i), but I have to confess it has frustrated me endlessly..

The reason we believe in WordPress is the “Fun” part of work- it makes putting content on your site so easy that it doesn’t feel like work. We’ve been able to get non-technical people to admin WordPress sites quite easily- can’t say that for Drupal, yet.