I really REALLY hope that this is just a resolvable bug not just a dirty trick!
According to BGR, Web Apps are running 2 to 2.5 slower than running the same App from iOS home screen.
Developers say that this happens due to old JavaScript engine in Safari browsers that affects Web Apps performance compared to Apps launched from iOS home screens.
I wish this is just a bug and not a foxy play to force developers to write Apps for iOS (Specially since Apple takes 30% off the sales revenue)