I got one of each. 128GB T-Mobile LTE on each one.
Same here, but AT&T. I've found a good use case. The mini is my get-out-of-the-house iPad. I transferred my unlimited AT&T data plan to it. My Air is my while-at-the-house tablet. So far it is working ok.
If I can avoid the static shock, the retina bleeding from the limited gamut Mini screen, the image retention while viewing a checkered image for ten minutes thing, the slowness of the Mini because its 100MHz slower, the missing PPI in the Air (264ppi vs 324ppi of the Mini), the heat of the Mini, the yellow tint, and the yet to be discovered flaws of each, I should be ok.