I've switched between the two platforms a bit - I had an iphone 3G, a few android phones, and switched back to iOS with iPhone 5. I really like Android but there were a few deal killers:

1) Battery life - pretty much the reason I switched back to iPhone. It doesn't matter how great the software is - if I can't turn on the phone it's useless. I don't know how many times I would be racing to meet friends at night, hoping I would reach them in time before my phone completely died. I spent an unforgivable about of my time tinkering with settings to extend battery using widgets (toggling data, location services, turning down brightness to the point it was barely viewable, etc.). My last phone was a Galaxy Nexus and almost everyone on my team had one. Guess how many people had 4G on? No one - the phone died in hours with it on.

A close friend, who is a diehard Android fan, keeps a stock of 3 charged batteries on him at all times (he has a separate charger). All of this was just too much of a hassle for me to justify. I haven't had a single day where my phone has died before I've gone home with my iPhone; it lasts a full day with my normal usage.

2) OS upgrades - I was debating between the Galaxy S3 and the iPhone 5 for my last phone purchase. Besides battery issues, a major con was that I knew the S3 would probably never be updated. Some of my favorite Android features are recent updates (Google Now) and it'd be painful to know that I probably miss out on new features for the 2 years of my phone contract. If the phone you want is a Nexus, this won't be that much of an issue, but that severely limits your device options. And it still somewhat applies to Nexus phones - the Verizon Galaxy Nexus is 3 OS updates behind due to Verizon's approval process.

3) UI/design - There is still a lack of UI/design consistency across the Android ecosystem. It means that the learning curve for the ecosystem is still higher than iOS and sometimes things don't behave the way you expect. Anyone who uses a combination Maps, Nav, and the back button heavily will feel this. I find that the Google Maps iOS app is significantly more consistent than the Android version (although less powerful). This is a consistent theme with iOS vs. Android - better UI but less power.

4) Camera - The camera is one of my most frequently used applications and Galaxy Nexus camera was pretty bad; Google sacrificed camera quality for shutter speed. There are a few Android phones with great cameras (S3) but they are not part of the Nexus line (see #2)

5) App polish - There is still a gap in the quality of applications on the two ecosystems. This is due to many developing on iOS first and Apple's review process. This is a minor complaint since the gap is narrowing and I expect this advantage to be gone by the end of 2013.

6) Maintenance & Depreciation - Have a cracked screen? Good luck finding a shop that will replace your phone model at a decent rate. Screen replacement on my Galaxy Nexus was $100+ while you can easily get your iPhone screen replaced for $30. Depreciation is a "feature" many don't think about, but it's nice to know that I can sell my phone for a decent rate if I switch back to Android (http://priceonomics.com/phones/)

I'm still a big fan of Android and will probably switch back when there's a Nexus phone released with a solid battery & camera.