Both Back cam has 8mp the only different is the f-stop (4s is a f2.4 / iPhone5 is a f2.2 making it slightly better in lowlight situation).
The 4s front cam has 0.3 mp and iPhone 5 front cam has 0.9 MP
*if you have an app for brightening photo as well as color correcting you can get away with the back cam situation, but the front cam is slightly better*
