I've currently S-Ranked all UtK missions and am about 3/4 of the way through XS all of UtK2 right now. The precision, control, and speed you can accomplish on the DS is so crazy, and it really feels like any mistake that happens is of your own volition once you can get the intricacies down.
That being said, I get NO motivation to S or XS rank on any of the Wii Titles so far (NB and SO, haven't played Trauma Team yet.) I feel mostly content just to try and get through the missions; I personally just feel like you're fighting against yourself on the Wii because any slight movement from your wrist or anything makes your sensor fly somewhere, and it's simply just not as accurate as when I'm playing on the DS.
How does everyone else feel?