Better battery life, smoother shape, Start and Select buttons below the face buttons where they belong, more built in storage space, a better web browser, Automatic wifi connection, 3g/4g compatibility... the possibilities are endless.
I personally don't need a second analog stick. That said, I want it if more games come out that benefit from it. So far, the only game that seems to benefit greatly is Metal Gear Solid 3D, a remake.







