This will always be an eternal match! Until you try both, most people don’t have time to loose, so they end up confused, not knowing which they will choose.

From my experiences I found WordPress a lot easier to make plug-ins than in Joomla! to make any kind of extension. Just check my Contact Form in the Contacts page, you can make one yourself just by knowing something about the WordPress hooks, what they are for and when they are invoked.

In the other hand, in WordPress the templates need more work than in Joomla!, the good thing is that you can customize them a lot more!