I get a lot of emails and comments about my "WordPress is better than Drupal" talks, presentations, videos, slide-shares, and rants. But believe it or not, I'm on Drupal's side! This post started out as a reply to one of those emails, but I feel it would be better to say this once to the world, rather than over and over again privately, in email.
The biggest difference between WordPress and Drupal, is that Drupal is a Content Management System, and WordPress is a blog engine. This means Drupal assumes that there will be many different kinds of users with various levels of control who are administering a website, and WordPress assumes there will be only one. This should be the deciding factor when choosing between WordPress and Drupal (or moving from one platform to the other).
Yes, WordPress is trying to move into the CMS space, because most people who started off as simply bloggers have realized that they need more than just a blog, but they love WordPress already - so why try something new? But the truth is, the more you try to do with a WordPress site, the more brittle it gets. The permission system is not very sophisticated, it doesn't scale very well, the theme system is a huge security hole, all content entered is treated in exactly the same way, database abstraction is weak, etc, etc, etc.
Similarly, Drupal would be complete overkill if all you wanted was a blog. The user 1 account will see way too many options on every page making the user interface overwhelming. Additional modules would need to be installed and configured to get exactly the same functionality as a WordPress blog, and considerable time would need to go into set up and configuration. And don't even get me started on looks - there are a limited number of beautiful themes for Drupal, most of which are already being used on thousands of other sites.
A lot of my original concerns about the Drupal content creation interface have already been addressed by the community - please keep in mind that my "WordPress vs Drupal" talks show a demonstration of Drupal 6. Drupal 7 is different! Drupal 7 does a lot more out of the box, and also provides a "Standard" profile option during installation which will cut hours off configuration at the begining of a project.
There is, however, still no one place to go to find out "what Drupal does" or why anyone should choose it over WordPress - or any other software solution for that matter! This is a problem that still needs to be rectified, and we do have a team of hard-working people redesigning the Drupal.org website, trying to solve problems like this one. The reason there is no clear answer to this question, though, is because the answer will be different for every project. With WordPress, there is only one or two ways to solve a given problem. With Drupal, there could be an infinite number of possibilities, and thus, an infinite number of ways to answer the "why choose Drupal" question.
The reason for this is buried in the roots of each project.
There is a single direction of development on blogging software, with the community deciding what should go into the "best blogging platform" and that is now exemplified by what you get with WordPress. What makes a "blog" valuable is going to be the same - or at least very similar - for every blog, so it's much easier to create the perfect software solution for a single use-case.
Drupal, on the other hand, does everything: blogs, forums, e-commerce, CRM, intranets, social networks, news aggregators, wikis, photo galleries, restaurant review sites, etc, etc, etc. If you can tell me what kind of website you want to build and what features you'd like to see on it, then I can tell you why you should choose Drupal over WordPress. What makes a "website" valuable is not what it does that's exactly the same as every other website, but what makes it different. Drupal is really good at all the little things that would make one project stand out from the rest - but because these differences are important, time needs to be spent making each Drupal site different from all the rest.
This is also why there is a shortage of beautiful Drupal themes. The kinds of companies and organizations that invest in the development of a great Drupal theme realize that there is value in having a unique Brand. Blogs, on the other hand, don't rely so heavily on branding for their success. It's about the blog content or the person writing the blog, not their logo or color choice that sticks in the minds of the visitors.
In short, WordPress and Drupal are still two very different beasts. We do have some things in common, and I still believe that our two communities have a lot to learn from each other. Fortunately this is the world of open source. The code is out there. All we have to do is look!