This is a great explanation of why mobile web apps shouldn’t simply try to emulate a native app:
Users of pretender apps get an experience that falls squarely in the uncanny valley — it looks like a native app, but something isn’t quite right. Perhaps it doesn’t respond as expected or it doesn’t quite follow the conventions of a native app. Often pretender apps have both of these problems and then some. They simply don’t feel “at home”.
Another problem which we’ve heard in usability: non-iPhone users are put-off when they encounter mobile websites that “look too much like an iPhone”. There are interaction problems: should the Android user tap the glossy button or the hard back button to move to the previous page? There are also visual design problems: when a page screams “designed for iPhone,” non-iPhone users feel like they’re being treated as second-class citizens. Not good, considering that many users consider their choice of phone to be a mode of self-expression.
Recommendation: Focus less on “I’ve fooled them all into thinking this is native!” and more on “This is a great user experience.” A few tips:
Keep it clean & quick to load (consider your use of images, animations, etc.)
Streamline key workflows: keep in mind that each time the user navigates to another page, they run the risk of encountering slow load times
Optimize layout & visual elements to be appropriate for a small screen size (look to native apps for best practices about font size, line height, tap area, etc.)
By default redirect users to the mobile-optimized version of your site, but include a link to the full version of the website