If I get one which should it be a Wii or a DS?

You should get a Wii because games for consoles are better than hand-held games.

Metal Triforce : I don't think you've played many games then.

I would personally go for the Wii because of its movement games like Wii Sports. You could at least get a little exercise and have fun at the same time. Plus, it does have some great games besides that.

It depends on what games you like to play. I personally would get a Wii because I'm not a fan of DS. That's just me.....

The real reason I what a ds is because of the Pokémon games

Well, I own both gaming systems, so let me highlight the epic stuff about both of them.

First, the DS. 
    You can carry it to anywhere you want to go! The battery life is actually great, compared to PSP.  It also have a touchscreen, which animates up the game even more, making it even more fun. The DS also is the current hand-held game for Nintendo to release their Pokemon games to. There are also a lot of different kinds of DS, such as DS Lite, DSi, DSi XL, even the most newest of all, the 3DS! The graphics are also good, but not great like the Wii, but great for a hand-held console with a touchscreen.

Now, the Wii.
    It's a great system to play with. You get to be active while playing games, and even have fun with friends automatically! Unfortunately, you cannot bring it anywhere, only to areas that does have a TV with the required plug ins. It doesn't have as much fun games like the DS, and the game selection is basically game boards, "get fit" games, sport games, etc. Nevertheless, it's a great system to own! It does have Legend of Zelda: Twilight Princess, and Legend of Zelda: Skyward Sword. (not sure if that's released yet!?)

My advice? Get them both.

You should really get Wii the motion games are a lot of fun like Wii sports resort would be a good game to play and it's really fun for the family too

The Wii would be a good console for a family or if you plan on playing with friends. There are some good single player games for the Wii, though, like Twilight Princess. The DS is boosted by an extensive library and portability, though. And it's much cheaper.

You should get the Wii because there are more games on it and it does give you some exercise and most Nintendo DS game are adventure games and can be finished quickly so then you might get bored quickly.But I also like the Nintendo DS because of Mario and Pokemon.