It's hard for anyone to adequately answer the program without knowing more of your requirements and experience. For example, the answer might differ is you said you wanted to do an eCommerce site versus a product review site using microformats.
The simplest of the 3 is probably WordPress and the most difficult is Drupal. But that doesn't mean Joomla wins by default because it falls in the middle.
The other point to consider is where each is in their development cycle. In some regards, they are moving to become frameworks and similar in functionality. I know Joomla is planning a new release which has improved functionality.
If I were you, I'd talk to users of each platform and ask them questions based on your requirements.