Give Mozilla a little more time. A HTML5 stack can be as efficient as a Java language based stack (Android, older Backberry, etc). It's all about the Javascript

Give Mozilla a little more time. A HTML5 stack can be as efficient as a Java language based stack (Android, older Backberry, etc). It's all about the Javascript JIT VM, the web render engine and how efficient the JS code is. So with the upcoming multi process Servo web render engine coded in Rust, FirefoxOS will have an competitive advantage in future. HTML5 based shells/"OS" have certainly a bright future (ChromeOS is already popular and there is WebOS running in newer LG SmartTVs). A HTML5 based windows manager for Linux/Windows are probably the next thing - that allow offline web apps and native GUI applications to run next to each other and with the windows being actually HTML iframes.