Too many too count, but to name a few:

• Wordpress is very bulky, Craft outputs ONLY the code you want/need it to.
• In order to achieve custom non-standard functionality in wordpress you must hack it, with Craft you simply build exactly what you want, how you want it, no hacking, no bastardizing a blogging platform, just good clean code.
• Craft is faster
• Craft is more secure
• Craft has a smaller, but MUCH more skilled developer pool.
• Yii
• Twig
  ...and the list goes on forever.