I have an Android phone and an ipad. It's very clear after a little use that the ipad is "snappier" (and animations are smoother etc), but iOS also feels very very limiting by comparison with Android. There are so many little things that Android just does right, that iOS...doesn't.
So which is more important, smoothness or functionality? I suppose it depends on the person and how they use the device... but really, I'd like both... :]
Namely..?
It's very possible that there's a difference, but it simply isn't large enough to be something that even registers for me - when I use my device my attention is not on trivial stuff like that. There are annoyances and things I notice lag, but touch response or menu scrolling just are not amongst them.
I think people here are significantly overestimating how much most people pay attention to these things.