Microsoft as usually – 10 years behind :) Apple used PowerPC in 2004, then moved to x86, and now iPad runs on ARM. So next Xbox (2020) will also run on ARM :)
Don’t know about Windows Phone, but with iOS you can change UI as much as you want. Just jailbreak your phone (3 easy steps) and look for skins or UI residigns in CYDIA. And I don’t talk about diferent icons. There is theme witch will make your iOS look like Android, or Windows phone, or something futuristic.
You can always jailbreak older iPhone and install custom made firmware. And it works on all iPhones. And for example Android ROM have to be for specific Android devices, so you can’t possible have ROM for every Android phone. That’s why Android sucks, ‘cause if you don’t have Samsung or HTC flagman – no one cares to make ROM…
P. S. There was always more possibilities with iOS, ’cause hacking/rooting/jailbreaking community is way more bigger in Apple family that in Android. Just look at how many hacks and tweeks Cydia has to offer. iPhone will be more friendly to any hacker at any given time, ’cause there is real unique tweeks, not only keyboard layouts and wallpapers like on Android.