This is very strong evidence that when performance matters to your iOS app, you are better off going native and not HTML 5.
Who here thinks that Facebook should have stayed with HTML 5?
Who here thinks that Facebook should have stayed with HTML 5?
I read the story on FB newsroom. I see that site is built on OLD asp.net webforms. Not even asp.net MVC. If their devs are constantly using the oldest of tech to create their site, it's no wonder their shit performs so badly.
Now I have no idea or backstory to why they choose these routes, they most probably simply didn't have any developers with enough experience or skill set to use newer better performing tech (I hear it's hard to find good developers).
Do you work on an HTML5 cross platform app everyday like FB engineers did? Guess what. That's when shit gets really tricky and hard.
It could be that they could never get true native speed without writing it natively. However, in my experience their HTML version was so awful that I suspect a lot of it was from bad decisions on how to use HTML5. That may be the problem though: that it takes deep knowledge to know how to leverage it correctly and speedily.
That said, my greater concern isn't performance on HTML5, it's interface. iOS, Android and (particularly) Windows Phone have very defined UI metaphors and design styles that vary a lot- if you have to replicate all of them then it removes a great deal of the benefit of a cross-platform app.
The answer may be, weirdly, in C#, using MonoTouch and MonoDroid. You'll always have to tailor UI to each OS, but having an entirely consistent backend to that UI is an attractive option. I just haven't managed to convince myself to drop the cash on a license yet, though.