they are coming up with a new iphone in a couple of months.. wait and watch. S4 on the other hand will get outdated in a couple of months as well - samsung and other andy counterparts release phones with uselessly large camera megapixel, hdd and ram every month.
iPhone. I would recommend the 4S of all models considering it's battery is decent. All models after the 3 are bad with drainage but the best for when you need it most would be the 4S. The iPhone 5 is nice also, although I haven't had one myself.