Why should I use Cortana over the Bing app?

While this app works, the Bing app does much more than Cortana on the iPhone, not to mention looking better to boot. My interests show on the Bing app as well, and Cortana cant be as ingrained into the OS as Siri because of limitations.
I hope it gets better, but for now Ill stick to the Bing app.

SmartiesPantsu~ about Cortana