I use CMS's and blogs on a daily basis. My favourite CMS is most definitely Drupal, but i do find there built in blog lagging behind Wordpress. Wordpress out of the box is brilliant and it is so easy to use for the novice who doesnt have any technical knowledge. Being a Web Developer/ Designer, i find it extremely important that the end user (client) will be able to navigate and update their website easily and without my hassle. I find the backend of Drupal quite confusing for the end user and a number of clients have complained how difficult it is, to navigate around and make changes. The same can be said for the blog of Drupal.

1. First off the blog module is very basic and doesnt offer all of the extra stuff Wordpress offers.
2. The second thing is that it takes the theme of your existing website and cannot be changed. Some people would like a different design for the blog.
3. Navigation to the backend where the blog posts are, are difficult to find for none techies.

It does have advantages:

1. Multiple blogs and multiple authors
2. Drupal is free.
3. You can use the existing theme if you dont want a different theme for your blog.

Conclusion I prefer Wordpress as a blog, and Drupal as a CMS. It is each to their own i think. If i design a site, i use both and get the best of both worlds.