What apps do is add eas of install (app store), and usability (cache, use device sensors, do some offline tasks)
For a webapp the installation is "Add to homescreen" on a webpage. It then behaves like a native app, no address bar. Usability is tackled by modern browsers that allow webapps started like this to: - cache the entire webapp, and some/all data it requests. - run webworkers in background, (get push notifications, etc) - provide sensor access via APIs, (camera, etc) And to conclude, todays webapps respond FAST. They do everything the same way a native app does.
Ofcourse if your webapp does video transcoding or uses some specific OS feature it might profit from being native. But even then, its unbelievable easy to wrap your webapp in a shell that adds these functionality.
How do you think FB and other popular content consuming apps work nowadays? You are basically looking at webapps rendered in a shell that provides the few APIs a browser doesnt yet have, like share button and contact/calendar integration, to get/set data specific to/on your device.