Now that we have a good Google Maps solution on the iPhone that supports voice-guided navigation, along with a new Gmail client that rivals what you find on Android, the choice to go with an iPhone over an Android device becomes even clearer.
I use all mobile operating systems because I like to test them out and give them a chance to earn a spot in my pocket. While I am an Exchange user in my day job, I also use Gmail extensively and always found the Android experience best for Gmail. Even though I have tried lots of different GPS navigation solutions, I invariably go back to using Google Maps 99% of the time. These are both now excellent applications on the iPhone. In addition, I find that the iPhone beats Android in these areas:
Apps and services still come to iOS first in many cases and in some instances we still don't see Android apps (UP, Fuelband).
The iPhone's camera is among best of all smartphones, even without all the fancy features and options.
Updates come from Apple and seem to skirt carrier control. You can count on your iPhone getting updates for a couple of years, whereas your Android phone may never get updated even a single time.
It's a pleasure to visit a physical Apple store rather than a carrier store.
The damage warranty for the iPhone is actually worth it, IMHO.
The accessory market is vast, giving you broad choices at great prices.
I do like Android for widgets, large displays, NFC, and pushing the limits of technology, but if I had to pick just a single smartphone then the iPhone 5 would be my clear choice.