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.*