new to CI

[eluser]pocketmax[/eluser]
I've only been using CI for 2 days now and I'm really liking it. I browsed through ellislab and noticed they have something called expression engine. I have a few EE/CI questions...

1. What makes EE better then wordpress? I've been looking to switch my sites frontend to a framework and for the past 2 weeks I've been considering wordpress. What makes EE different from wordpress?

2. Since I'm starting to fall in love with CI is there any benifit to using CI for a backend and EE for a frontend?

3. Is EE built on CI? if not, why not? there made by the same company.

4. Can EE use wordpress themes? There are zillions of wordpress themes out there but I only found a few EE themes.

-Thanks