It's a toss-up in some respects. I think the iPhone 5s is best if you value camera quality (Samsung stuff tends to fall apart in low light), local media playback and gaming... and, of course, if you prefer a 4-inch screen. The GS4 has the screen size advantage, and if you prefer flexibility in both hardware and software (removable battery/storage, Android's looser policies), it's your pick.
I'd like to try the GS5 myself before pronouncing it a small update over the GS4... there's a few key updates present, including a better camera.
Could be...I have an iphone 4 yeah I know a 4 . I keep waiting for a larger iphone to help with my fingers. Camera????? my old iphone 4 has a better camera than any of them. Give me an iphone a little larger and better texting apps and I will never look for another phone. BTW I'm getting 32gb this time
Oh, you're in for a treat, then. The 5/5s are in another class compared to the 4. I suspect the iPhone 6 (or whatever it's called) will be a leap beyond that.