IPhone 4 with iOS 6 or iPhone 5s?

Which one should I get

Added (1). btw, I'm deciding between the two.

Neither, but iPhone 5s would last a bit longer since iOS7 runs like *** on iPhone 4 and iOS6 is deprecated.

It's clear, the iPhone 5S. The OP version doesn't make a difference, they are both compatible with iOS 7

Iphone 5s ios 7 run wonderful. Ios 7 on iphone 4(if you need to update can cause you many problems and definitely cause it to run laggy.) iphone 4 i would always keep it under ios 7.