Welcome to Wiichat, Kayla. Hope ya enjoy the forums.
I haven't played MW3 on the Wii or my 360, and I can't say I want to, but I doubt the experiences are all-that different. The only major difference I know is that the Wii version lacks killcam, IIRC, and no mics (no annoying whiny randoms, but no cooperative effort with friends...). Well that, and the controller differences.