I cant comment on win7 phones but have some experience with AOS and iOS. I am not sure whether I am "just a fandroid" or see Android really is at the beginnings of a future landslide victory but anyway my 5 cents worth :P
The main benefit of a iPhone (and i am only talking 4 and 4s here) is its consumer friendly approach, it is essentially a dumb smartphone. The wife has a 4s, it never misses a beat, does everything she wants, battery time is acceptable, camera is excellent, the only real negatives is she does find the screen small compared to her previous phone (3.8" vs 3.5") and uploading pics to facebook is a more painful experience than AOS. The 4s just reeks of WAF (Wife approval factor) and this for me is its ultimate selling feature.
I would never look beyond an Android device and to me its best feature is customization, that said on a 4 or 4s equivalent android the standard user experience is very livable and definitely not a negative.