Personally, I like the gameplay possibilities the DS offers, but I was somewhat disappointed in the Wii's motion control, or at least the games that use them.
You can't make me choose between the two, but if I had to pick a better one, touch. More games are making good use of it, while the only people attracted to the Wii are uncreative people looking for a quick cash-in.
While I still think that traditional control beats all, I think touch control CAN be used to the same potential, give or take. I mean, Cooking Mama to Phantom Hourglass, the possibilities are nigh-limitless. I mean, I was seriously blown away by how perfect PH's controls are. They use the touch screen, and the other DS features, to beyond their fullest extent.
Motion control is good for SOME games. Animal Crossing benefits a TON from it, and Super Mario Galaxy certainly uses it well, but above all else, I think it's best as, how do you say, as another button. You know, not as the FOCUS of the controls. It can't hold a full game - or at least, not yet. Touch controls can.
I got a chance to test it recently. It looks sexy, and weighs a lot less than the phat. The menu looks great, the screens are a bajillion times brighter, the sound is crisper, and the cameras don't suck as much as I thought they would.
One thing I HATE about my DS is it makes this constant eeeeeeeeeeeeeeeeeeeeeeeeee noise if you're listening with headphones. So, whenever music stops for dramatic effect (etc) instead, I get "eeeeeeeeeeeeee" instead... Another phat I tried this with also did this. Do all phats make this sound?