iOS 5 is better than the previous iOS in many features. But how better is the iOS 5 than the iOS 4? The guys at New Relic compared the web browsing and the apps speed on the iOS 5 and iOS 4 using the same iPhone hardware to know how much improved is the iOS 5 than iOS 4? You can see the result of the test in the below image.
iOS 5 vs iOS 4 Speed Test
As we can see that iOS 5 is much better and faster in terms of the speed than the iOS 4, specially for the mobile optimized web pages. So, here is the one more reason to upgrade your iOS from the iOS 4 to the iOS 5. Cheers :)