The main difference between the two platforms is one has synergy and the other does not (kind of). Another point to consider is how much do you rely on the cell vs other electronic items (laptops, PC's, tablets, etc).

Personally, one thing that was most important for me was to have (what I consider critical) data available to me regardless of device, connected to the world or not. iCloud filled that need for me.

Another thing to consider is apps by platform. Additionally, do you care to deal with fragmentation or not.

And finally - is it pretty? lol

Side note - For Android phones - HTC hands down. Build quality is by far hands down better than the rest.
S4 is a cool phone if you are into plastic.
iPhone 5s - depends what you are currently using... 64bit processing is kind of cool on a mobile device, but moot if the resources are not present to take full advantage of the processing speed.

I feel like I may have not helped you out here much, but it's just one little opinion to get the ball rolling for you. Good luck deciding.