I'll agree with you that not having the Grim Ripper or God of Rock in the Wii version is a downside, oh well, at least we have MetalHead and Eleroy Budvis (or Tom Morrelo, as of this point I'm stumped)
There have been rumors going around that the Wii will have downloadable content via Wii Shop Channel
It actually makes me feel more into the game with the sounds comming from the guitar
Also, the notes sound more simalar to the First, Second, 80's on Wii and PS2
Oh, and yes, Wii has online play, and it's easier to find matches on the Wii
Short Summery 1# Wii
2# 360 & PS3
3# PS2