The basis of my personal preference for the iPhone boils down to aesthetics and to the ecosystem.
In regard to aesthetics, I just think that the iPhone has a more elegant GUI. It does not have the flexibility of Android, but honestly there's not much I would want to change about iOS anyway. Perhaps quick toggles for turning on/off WiFi etc. would be nice on the search page, but for me that's about it.
In regard to the ecosystem, I might surprise some by saying that iOS's links with the App Store, iTunes, and OS X are only a secondary concern for me. My primary issue is that Google makes money from information collected from Android users. The mobile phone user in the Android/Google ecosystem is not the customer - advertisers are. For me, that's a huge disadvantage of Android that can't simply be argued away by massive Samsung screens or widgets.
In any case, there are only limited ways to use a mobile phone. I expect that over time basic functionality on all phones will be pretty much the same, with only hardware quality and GUI seperating models from different vendors. If Apple keeps iOS elegant and they maintain high quality control (there are signs that they are slipping), then I probably stay with them. If not, I would consider Microsoft's mobile OS.
