A major difference between the NGP and 3DS lies in the two devices' touch-sensitive technologies. The 3DS will reuse the original DS' resistive touch screen, whereas the NGP will have two capacitive touch areas (front and rear), of the type most tablets and smartphones use today (including the iPhone and iPad).
The 3DS' resistive touch screen requires some depression (hence the stylus), but can also respond to a finger press. The technology offers a nice level of precision (like when handwriting or pecking at small virtual keys), but certainly requires a bit of a learning curve when being used in tandem with a stylus.
Gaming feature: Little Deviants gameplay on Sony Next Generation Portable
With the introduction of the NGP's front and rear touch capabilities, players will essentially have another dimension of interaction at their disposal. At first glance the rear pad might seem silly, but after the insightful video to the right, we're beginning to think it might actually provide a more seamless gaming experience. The video showcases a game called Little Deviants, in which the player drags a finger across the rear panel to manipulate the world onscreen. We're excited to see that for the first time gamers can interact with a portable gaming device without their fingers blocking the screen.
Sure, the NGP still has a front touch screen, but instead of a stylus, players will use their fingers for interactivity. Though it seems like that will reduce precision, it also means we won't need to hold a pen while gaming. Capacitive touch makes handwriting difficult, so the Brain Age-style games found on the DS will probably continue to see their success on the 3DS platform.
Let's be clear, we're not trying to crown one technology as being superior to the other--in fact the two separate mechanics will most likely create an even bigger divide in the software available for each system.
It's certainly refreshing to have a game-centric device feature a new application for a capacitive screen--after all, we've been clamoring for gaming buttons to complement the iPhone/iPad capacitive screen for a while and now it seems the NGP will allow for the best of both worlds.