iOs 5 will be the deal breaker. Sure I love the large screen, but there are many things in android that are not in iOs like improved notification system, widgets (that I use daily) full blown google search with voice command. (meaning you can search for anhything, not just "call home" or "Play Red Hot Chili Peppers", but rather "Find Portland, Oregon" and it will bring up the maps app, or "Find closest Hamburger joint" and boom! it will find it with a google search or even ask you what program. (Like on my phone I have not only google search, but I also have Yellow Book, so I can find that closest burger joint via the yellow pages on my phone and yes, it will do the current location deal)
I do agree some phones get updates later on and that can be a pain, but that mostly has to do with the skins the manufacturers put on and trust me, the stock android sucks big time. HTC Sense is about as close to a rich UI ad you can get besides iOS. Just wish the screens on the HTC phones were as good as Samsungs.
as for the apps, its not that they are behind, its just not many developers want to develop for Android. From what I heard apps on android can be a ***** to develop and the fact it uses google check out rather the thing on Apples side.
If Apple can develop a larger screen phone along side the 3.5" model, and improve many things in iOs 5 I may switch, but key things like the large screen, and some of androids rich features are keeping me with my EVO.