Android and many of the OEM's have come a long way. A number of Android flagship devices ever since last year have surpassed the legendary iPhone line and precocious iOS in practicality in both hardware and software after five years. After 5+ years, Android and its OEM's simply matured. Android devices were ugly ducklings in its freshman/sophomore years only to turn into a beautiful swan its senior year.
Form factor, excellent design, games, and camera might be the only benefits for me going back to iOS but that still might not be enough. Apple is great at the holistic experience. Integration with software and hardware. But I don't want to be locked into an ecosystem. Smooth is nice but is it worth trading less smoother animations for more features, flexibility, and customization? Eventually iOS slows down after every update and needs fresh restores to recapture its early fresh speed again.
If you believe Apple knows what is best for you, stick to iPhone. If YOU know what is best for you, try Android. After three years with iOS, I got bored. After three years with Android, I'm still learning news things with the OS and its versatility has prevented me from ever going back to iOS. Android isn't perfect but it might already be the greatest mobile OS I have ever used. Starting below iOS, Windows Phone, and webOS at first before surpassing them all.