Unrealistic micro-benchmarks aside, I've yet to find an Android app written using HTML5 and JavaScript that feels anywhere near as smooth and efficient as native apps written in Java. I suppose I don't have numbers to back me up, but I'm not sure that really even matters. The performance difference is something that users notice.
Those companies have an agenda to sell regarding HTML5 development
They do. However, don't be so quick to dismiss the point they are making: on high-end devices at least, html5 apps are at least as good/performant as native apps.
By the way, Apple, Google and Microsoft each have an agenda as well: to enclose developers in their walled garden, making them learn and use proprietary non-cross-platform APIs so that apps can't achieve a "ship new features everywhere, at the same time, easily" approach. They also want you as a user and a developer to abandon your phone after a while by deprecating APIs and making the OS effectively non-updatable, and making it very hard to update manually (do you know how to port Cyanogenmod to your device? Fix its bugs?).
as soon as your target middle to low end handsets it is turtle speed time.
... on Android. It probably isn't great on low-end or old hardware (although light pages should still run fine). However, Firefox OS is designed and optimized for running those webapps on low-end hardware, contrary to Android.
Which vendor do you trust to make the web fast? The ones who have nothing to gain from it, because they wouldn't be able to retain users anymore who could switch to a new OS in a heartbeat if all the apps were webapps? Or the vendor who made huge contributions to the open web?
