iPhone vs iPad Mini vs iPad for Gaming

So I currently own a Nexus 4, however I'm thinking to upgrade to a new phone and tablet combo. I want 1 device from iOS and 1 device from Android, however I'm really stuck between what to get (I want everything basically lol).

But I have broken it down into 2 main things I want to do now, gaming and all the cool apps on iOS, most of my productivity and communications and video playback on Android.

So I was looking at tablets and video play back would be really great on this, and it pushed me towards the next Nexus 10, however I then thought gaming would also be great on a tablet so this is my question.

Which iOS device is best at gaming?