The Great HTML5 Mobile Gaming Performance Comparison
This Post from Scirra, the makers of Construct 2, is liquid gold for HTML5 Game Developers targeting mobile (which is probably all of em) – it shows the performance of a particular game built in Construct 2 on various devices in various deployment methods, including straight Browser (Mobile Safari, Chrome for Android) and package as an app (PhoneGap, DirectCanvas, CocoonJS)
Takeaways are that iPhone 4S and iPad 2+ are pretty handy at HTML5 Games, even just running via mobile Safari while Windows Phone 7 and Android still have some work to do performance-wise, although Android native w/ CocoonJS gets back up to an acceptable 34 fps.