3DS homebrew can be launched straight from the home menu,
3DS homebrew has access to the circle pad which could be used as a wireless joystick,
3DS has a larger touch screen, which gives a better virtual keyboard,
3DS has much better WiFi support than the DS, which is limited to either no security, or WEP (which is almost just as insecure),
The result is 3DS Controller: an open source, configurable, 3DS homebrew application which allows you to use your 3DS as a wireless controller for Windows.