I’ve seen a few reviews for the Wii already and they’ve all said the motion sensor is just a gimmick and in most games it’s too difficult to be precise.
The price difference may help it, but I don’t know.
I think the big unknown is the whole blu-ray vs hd-dvd thing. If blu-ray emerges as the standard, and the PS3 supporting blu-ray is a big step in that direction, then the PS3 will probably do well. If blu-ray becomes the next beta-max I think the PS3 will be in trouble.