I'm pretty sure the only major feature that would be taken out, would be the ability to make user content, and to share it (if there is any of that in this game to begin with). All the stages of evolution will be there, as that's the point of the game. I really don't see them taking out the space portion, for example, because that's one of the major five components. Graphics will obviously be lesser on the Wii version, but that's not really taking any of the meat out of the game.
The DS version will be the one that gets stripped down IMO.