I found a 32GB space grey 5s today. Call your local Best Buy if you’re still looking for one. You might get lucky too. I’ll try to do some comparison shots with my old iPhone4 soon. I already snapped one in my car in a dark parking garage. The 5s smoked the 4. The images were both very grainy, but the dynamic range was significantly better in the 5s…as expected.
Also, the iOS7 camera app sucks on the smaller screen of the 4. It was designed for the 5 and 5s. I was very annoyed that it blocks part of the viewfinder now so its hard to line up a shot. I’m sure they will address that in a future update.