Yes, hardware keys are allways better.
But specialkeys as virtual keypad are better (faster) to handle.

Accelerometer is only funny, if you play on an extern monitor.

Onscreen buttons: It's a no-go !
Have you seen the game demo from Windows Phone 7 , The Harvest ?
Most times, you see fingers in front of the screen. That's not funny.

Btw, if I start uae4all, I can start kick.rom with sixaxis buttons.
Why isn't it possible to use the mapped buttons on the keyboard ?