I can't speak for Windows RT and Windows 8 because I haven't had a chance to use either extensively but I have used Windows Phone 7(.5).
In the past six months I've gone from a Samsung Focus to a HTC One X to a iPhone 5 and back to a HTC One X.
Despite running on seemingly antiquated hardware, the Focus and Windows Phone 7.5 was just as fast and reponsive, if not more so than the other two devices.
In the past six months I've gone from a Samsung Focus to a HTC One X to a iPhone 5 and back to a HTC One X.
Despite running on seemingly antiquated hardware, the Focus and Windows Phone 7.5 was just as fast and reponsive, if not more so than the other two devices.