Well, for one, when you're embedding UIWebViews in your own app, the JS engine disables JITting to native code. Apple will not sign and grant 3rd party apps wr

Well, for one, when you're embedding UIWebViews in your own app, the JS engine disables JITting to native code. Apple will not sign and grant 3rd party apps write+execute memory permissions, making it impossible to build a JITter. So only "MobileSafari.app" get "native javascript performance".