I can only go by the experience on my S2, but I would say there isnt any responsiveness difference between recent Samsung Android 4.1.2 (TouchWiz) and pure Google AOSP based Android up to 4.2.2 (e.g. CM10.1). At an OS UI, system menus etc. level they're pretty much equal and largely on par with my old iPhone 4.
But Apps on Android are completely different story. Some are downright dismal in comparison to a same-era iPhone, for example Tapatalk & AccuWeather which are smooth on iOS, but stutter noticeably on any version of Android I've tried. My current iPhone 5 is however in a completely different league compared to the two, everything just glides like silk.