That depends on if you want your application to take advantage of specific properties of the devicies or facilities available with the OS version supported on the device. The 9550, for example, is a touch device while the 9700 isn't. There are two broad strategies: 1) write your application to the lowest common denominator (OS and hardware0; 2) write you application to make maximum use of the facilities available on each supported device. So, yes, you can write one MyApp for both devices if that satisfies your goals and users.