I don't see either as a "Pro vs Con" thing.
iPhone: Locked into the Apple ecosystem, and your phone works nicely, but is severely locked down. The plus to this? All your updates generally will be well known when they come, and if your device will support it. Being locked down means fewer problems possible, generally speaking.
Android: Locked into (Sorta, kinda) the Google ecosystem. Stock, most of the phones are garbage (Not Google's fault, carrier's fault). But, you don't have to stay stock, and can do all sorts of things with your hardware (At your own risk). Being very open, means susceptible to more problems, but also more possibilities are there.
Do you like to tinker with stuff? You'll feel "jailed" by an iPhone. Don't care to tinker much, if at all? iPhone might be the best route.
Have you bought into the Apple ecosystem (You love iTunes, your house is full of Macs, etc)? The iPhone will fit nicely.
Have you bought into the Google ecosystem (You love Gmail, Google Apps, Google Voice, etc)? The Android device will be right at home with you.
Do you like a choice in form factors, looks, customization? Android fits the bill.
Do you like not having much choice in form factors? Nothing wrong with that, if you just want one line of phones, one line of tablets, etc. then an iPhone will work very nicely for you.
Who will get the most market share? Android OS. Just because of how the market works. With more choice, comes more vendors; just like Wintel vs Apple. We saw how that worked out.