We have recently tested some HTML5 content with heavy javascript libraries from an iOS app. The app designed to load these contents in UIWebview. iOS 6 was used for this testing. My team did not observe any noticeable performance issues against mobile safari browser. But on the web and in other stackoverflow discussions (like this one - link) experts claim that UIWebview misses Nitro Javascript Engine so it is usually much slower than Mobile Safari Browser.
Is this no longer an issue with the latest versions of iOS (6/7 beta)?
Is there a way to benchmark and observe the performance difference between UIWebview and Mobile Safari Browser?