Primarily I'm keeping the Mini because the size works for me and despite the Mini falling just a bit short of the Air 2 (IMO), I think this was a terrific update overall for the Mini (i.e. Not as many compromises to accept as there were with previous versions).
My iPad history: iPad Original (9.7), iPad 2, Miini Original, Mini 2, Air Original (i.e. After balking on the Mini 3), also used Air 2 (my wife's).
I travel for business (4 days/week) and the Mini size just works for me on the road, where I find small and light to be a major asset. Where do I feel the Mini falls just a bit short of the Air 2? (Personal/subjective observations):
-Display: Colors don't have quite the punch (i.e. Not quite as vivid/saturated), but appear to my eye to be a much fuller gamut than previous Mini's and appear to be accurate.
-Battery Liife: I'm finding the battery drains more quickly than the Air though not enough time with it yet to quantify.
Performance: I mentioned another post (above) that some animations on the Mini appear to be choppy/jittery ( i.e. Just not quite as buttery smooth as the same animations on the Air 2). Scrolling the open apps is one example. Seems logical to me this could be due to the A8 in the Mini vs A8x chip in the Air 2 (i.e. better graphic performance of the A8X). Seems to me the Air 2 could have a bit more longevity to better handle future IOS updates due to its having the A8x (purely speculative).
All in all though, I'm happy with the Mini 4, think it was a terrific update and am okay accepting the few (perceived) compromises listed above. But, the main reason I'm keeping the Mini is because the Gold Mini and Midnight blue cover combo is killer. Can't get that on the Air 2! Seriously though...the combo is awsome.
Thanks a lot mate. Any compromise on split view compared to air 2 ?