ipad mini retina 128gb verizon. Black.
Screen will be much sharper (higher quality) than ipad air. Same internals. More portable. Plus it's cheaper. This isn't a very hard decision.
The ipad Air really brings nothing new to the table experience wise. It's a bit thinner and lighter. But it begs for a case so it's not like it will significantly change how you use it (compared to ipad 4). With a case, it's still bulky and over a lb. Even Anandtech said with a case, you still need to prop this tablet against something. Speed wise, you probably won't see much of a difference from the ipad 4.
On the other hand, the retina Mini will be a very significant upgrade. Instead of struggling to barely run the OS, it will fly. And it will have possibly the best screen available on a tablet. That's the remarkable thing. Going from the crappiest screen seen on a tablet to the best.