The problem with instant release is that it hits you all at once, while an XR give a smaller instant release and the trickles out the rest. As a result, it tends to be smoother. Vyvanse due to the way it is metabolized is even smoother. The same amount in an Adderall XR will last twice as long and Will have less effects then the 10. You can also get it in a 5mg XR.