3 reasons 1 for each.
1. Welcome emilie222! Thats pretty simple.
2 the Mysims for the Wii has more control over how your sim does stuff ands easy to pick up the pieces with a remote rather then a stick.
3. DS hads minigames which make it a little more action like finding fish, etc.
Go for the Wii becuase i like the sense of a control through the remote better.