Admin interface is constantly being iterated on to remove unnecessary legacy features and to streamline the interface. Resulting in a very clean and easy to understand interface that also offers a wide range of options.
Drupal can be customized to do almost anything. It was built ground up with the intent of using a wide variety of small modules to get the exact result wanted instead of just the most common solutions.
Drupal is not easy to get into and out of the box doesn't offer much. To get Drupal doing what you want it to, modules are required. To get modules, an understanding of how Drupal works is required. And that takes time.
The default WordPress SEO setup will work great for most people starting out, but you can further tweak different aspects of WordPress to achieve better search ranking results by installing plugins, following tutorials or experimenting yourself.
Partly because it is one of the most popular CMSs there are people actively finding security holes. Even though these holes are plugged by Wordpress regularly if you do not update your system regularly you may end up being hacked. There is also no easy way to rename access to the admin area so you...
If you have a low end server or lots of traffic it can be hard to get good speed. There are numerous plugin options for caching but most will only work with simple blog like pages and can be tricky to get working.