It's an uncomfortable game to play on the DS because of its use of both the stylus and the traditional controls, requiring you to switch back and forth between the two on a near constant basis. The game also looks pretty bad on the DS, with lots of chunky, pixilated sprites and textures, while the PSP version looks relatively crisp and clean, with richer colors and more detail. What really kills the DS version, though, is that the gameplay doesn't feel right. Movement feels stilted and worms can get hung up pretty easily on pieces of the environment, and the physics on a lot of the weapons are exaggerated, which can lead to frustration when a well-thrown grenade hits its mark, only to then bounce wildly away into the drink or, worse, next to one of your own worms.
It's hard to believe the PSP and DS versions were made by the same developer.
There aren't a lot of ways to play Worms: Open Warfare, though again, the PSP gives you a few more options than the DS. You can jump into a quick one-off fight against a random opponent on a randomly generated battlefield, or you can create your own custom game, defining the theme of the level, the level layout, and the participating teams. If you're looking for a bit more structure, there's a challenge mode that pits you against a series of increasingly tough and cunning opponents. There's some basic multiplayer support for up to four players as well. Both versions have the same modes of play, but there are some subtle differences that give the advantage to the PSP; for instance, though you can edit the teams in both versions, only the PSP version lets you create a whole new team, and the PSP version offers a more granular level of customization when creating your own game.
Neither version of Worms: Open Warfare is particularly ambitious, and you get the feeling that Team17 is simply testing the waters to see if there's still a demand for an old-fashioned 2D Worms game. DS owners get a pretty raw deal here, and the game is too rife with poor design decisions and unattractive execution to make it recommendable to anyone. If you've got a PSP, though, and you're looking for some light and breezy strategy fun, Worms: Open Warfare hits its mark.