Galaxy S4. It's better than the iPhone in my opinion, and I have managed to use mine to sway avid iPhone lovers, because my phone is better than theirs. And Android is destroying Apple in market share, because it's a superior system. There are many reasons the S4 is better than the iPhone......
1. Use your phone as a remote control for any tv or cable box with an infrared sensor on it.
2. You can transfer files, photos, etc. to and from another phone or device just by touching it to yours.
3. Ability to add an SD card for added storage.
4. You can actually replace your battery if it dies.
5. You can watch and stream 1080p HD video.
6. Larger screen.
7. Group Play app (look it up, it's pretty badass)
8. You can use the built in camera app to automatically erase a blurry figure from the background or make your own animated GIFs.
9. The front facing camera can track your eye movement to keep the screen from turning off while you read.
10. The same eye tracker will allow you to read something, and automatically scroll without you ever having to touch your phone.
11. It has a standard micro USB port to make it easier to sync and transfer with your computer.
12. You can find most of the common functions by swiping the top of the screen downward, rather than navigating through page after page of menus.
13. The speakers are phenomenally better, to the point you can use it as a stereo without having to hook speakers into it.
14. The keyboard is setup like a normal keyboard with both letters and numbers, instead of having to toggle between screens.
15. Air Gesture - read up on it, also awesome.
16. The hardware and software for the iPhone are horribly outdated.
17. MHL (I don't know how to explain it, just research it)
18. 13MP camera vs 8MP.
20. Destroying the iPhone in every review from techies and users.
It's all a matter of preference, but bias aside, the S4 is a superior phone in just about every single measurable category.
Come to think of it, the only advantage iPhone still has over the S4 is that accessories are in piles and widely available at any store that sells anything, even 7-11.