The Wii version is going to have new graphics during the operations, new procedures and new tools to poke people with. Stuff like that. It will also have an extended story mode. If you are getting a Wii, I would suggest waiting for the Wii version.
For the DS however: It depends on you really how much replayability it has. The story mode is fairly short. It can be beaten pretty quickly. You can go back and try for better scores after you beat the story mode though. I don't really think the game entails anything other then a story, and operating. It does have some pretty long dialog sequences though. I think you will be interested in it a lot until you beat the story mode. Then, how much more you can play the same scenarios over until you get bored is up to you.
I have never played it before. The above statement is just from information I have gathered. Someone can correct me if any of it is wrong.