> I've seen a couple of video running Mame4Ios and IFba and they run pretty well, and > they use pretty recent version of mame too...
Nope. MAME4IOS is the usual depressing MAME4All 0.36 version. A5X and A6-based iDevices can run modern MAME just fine (and their GPUs would enjoy the eventual GL port of the HLSL filters), but nobody's done that port. The only mobile modern MAME is MAME4Droid Reloaded, which runs 0.139 pretty nicely on Tegra 3 (and should be amazing on Tegra 4 and Exynos 5 devices).
Also, I'm kind of entertained at your certainty on those specs for the Mini 2 given there haven't even been leaks out of China about it yet.