What separates the DS version of Gunpey from its PSP counterpart is its Saturday morning presentation. Instead of slicky-cool visuals, you're getting an onslaught of colors and bouncy, toe-tapping tunes. There's some semblance of a story here too - something about a bounty hunter flying around and challenging other people to line battles. It's kinda unfair that they can use special moves against you (like causing the lines to rise faster), but you've got to set a good example and play nice.
As with any puzzle game, there's a two-player versus mode available over local wireless connections. The only other difference the DS game can boast is its touch screen interface, which does give you the ability to quickly slide the lines where they need to be. PSP owners are stuck using those crusty, Stone Age "buttons" to do the work.
Right now it looks like both versions of Gunpey have something unique to offer in the way of visual style - that's likely to be the only thing that'll sway you one way or the other when the game ships in November.