I have the iPhone 4S and a Google Galaxy Nexus and must say hands down I prefer the iPhone 4S. I'm a tech guy, I love all the new toys and the software to go with them. I thought the bigger screen on the Nexus was nice, but the quality isn't that great. Also the phone was too big for my taste. I'm 5'11, pretty much average, and the phone just isn't comfortable for me to use, specially with one hand. With my iPhone it fits into my hand so well and I can use it with one hand as if it was an extension of my body. The Nexus I find I after have to use my other hand, even for simple task.
Also the UI for Android just isn't that consistent. Sometimes you have to click on things at the bottom, which you can generally do with your thumb, but other times, what you were clicking at the bottom is not on the top, far right, and it's either an awkward stretch to get to it or using your other hand.
The battery life isn't very good, no where near as long lasting as my iPhone. Also takes longer to recharge.
Jelly Bean is nice, and it's a vast improvement over Gingerbread, which I used on an old Android phone. It's definitely much smoother as well compared to ICS. I would say that it really just comes down to person preferences, and would try them both out as some people enjoy being able to almost completely customize their experience. Also Android is catching up in terms of having the mainstream apps, the only thing I haven't been able to find on Android is a decent Twitter app. I use Tweetbot on iOS, for Android I've tried the official twitter app, Tweet Lanes, Tweedle, Plume and don't like any of them.
I find when a new Android phone comes out, I'll want it, and then another one comes out and I'll want that one, etc. etc.
It's much easier to getting a new iPhone every year, just sell the "old" one and that pays for most if not all of the upgrade cost. I purchased the Nexus from Google because I wanted updates as they were released and not having to wait months.
Other things I love about the iPhone is the amount of accessories that are available. All kinds of cases, car carriers, battery extenders, screen protectors. I like the Apple ecosystem and everything works between my MacBook, iPad, iPod with iCloud.
I would like to see the next iPhone have as nice a display as the HTC One X. If the HTC One X was available on the Google Play store, I would have purchased that phone just for the display. Two co-workers have that phone and it's just gorgeous.
Edit*
I hate the SMS default client in Android as well. It's so much better on iOS. And I can message my wife who's also using an iPhone with iMessage that works over wifi.