iPhone Charging Case

I am heading to NYC in April for the NFL Draft and was just wondering what the best case is for charging it at the same time. I will be out and about in NYC pretty much all day Thursday of that week. Also all day traveling Wednesday.

I know Mophie makes a few models of charging cases for iPhone5, but wanted some input on which one I should get?

I will need to know sooner than later as I want to get it purchased and test it out.

I'd look at the Mophie Air & Helium. They are very similar but the Air is slightly more expensive but has about 20-25% greater capacity.

I've not used the Mophie 5 cases but they've always worked well for my 4 and 4s iPhones