''Functionally the DS and PSP games are the same across the single-player mode, but the DS has the clear upper-hand when we come to multiplayer. Both games feature head-to-head play for two players, with the core invader shooting gameplay being turned into a battle mode of sorts, with each player able to send invaders over to their opponent's screen. It works really well, but is sadly much more limited on the PSP.
On DS you can play locally against someone without the game, locally against someone who also owns the game or over the internet against someone anywhere in the world. You also have online leaderboards so you can see how you rank against the world's best players. On PSP you're limited to local wireless play against someone that also owns the game. There's no game sharing, online play or online leaderboards.''