Aside from that, offline app cache is a PITA to implement.
Things have got better though. Web audio works on iOS 6, and Chrome on Android finally delivers a proper browser. I hope in a few years time we'll actually be able to serve games in WebGL to the browsers on both platforms.
Not true[0]. Home-screen web apps use the Nitro engine as of iOS 5. It's only embedded web views (i.e. the Facebook app, Google Chrome on iOS) that don't. FWIW Chrome is my favorite browser on iOS, despite the speed loss.
[0] http://arstechnica.com/apple/2011/06/ios-5-brings-nitro-spee...
We do actually download and stash most web resources, to speed up load times, so it's not completely window dressing. Our app is designed to be added to the Home Screen, but it also runs inside Safari or Chrome just fine.
I was on a project last year, and we built a mobile website (could work in iPhone/Android and probably winphone, but we didn't test). Got a lot of immediate "yeah that's great" from some people. Partners reached out for potential customers/sales - every single one returned with "where do I get the app".
Us: "http://foobarsite.com.
Them: "Cool, but I can't see where to download the app!"
Us: "You don't - you just go to the website"
Them: "But I need an app!"