It could be contrast ratio, colour gamut, brightness, subpixel quality, viewing angles, reflectivity of coating, susceptibility to oils/fingerprints...
(I haven't used either, I'm just saying)
The iPad Mini Retina will likely be the perfect small tablet for most users.
Android indeed has a "bigger" learning curve which make people more efficient in a short time for doing things with their phone/tablet.
Easy example, Tasker, Gravity screen, NFC and Autovoice...
I find that with the ipad mini viewing angles actually do seem kind of important, because—unlike a phone—I very often use the ipad mini without holding it, whether sitting on a table, on my lap, or propped up against something while I watch a video. The result is that one doesn't have nearly the same easy control over viewing angle one has when hand-holding a device...