Tama-Go.
This is just me, but Music Stars irritate me. The fact that everytime you leave it alone for a short period of time and it starts practicing it's instrument.. (which, in turn raises it's stress level.. which you have to work hard to get down.) just irks me. Also.. it doesn't do much as far as care. Most of it is focused on the band and such. I don't like that.
Pros of Music Star vs. Tama-Go:
*The size. It's much smaller than the Tama-Go.
(I can't think at the moment, though there are more..sorry about that.)
The cons of MS vs. TG:
*The base of everything on it is the band.. the care part is like, 25% to 75%
Tama-Go pros:
*Focused on care, like the older, classic versions.
*You can get more things, just by purchasing figures.
*You can do almost everything on it from the iD except it's in English.
*It's customizable! Make it your own!
Tama-Go cons:
*It's quite large.
*Not a "Pocket pet".
*The sound is muffled.
*The clear screen scratches easily.
*The figures aren't cheap.
*The keychain can't be trusted to hook onto anything.. it's too flimsy.
Don't choose just based on Pros/cons. The Tama-Go really is better, IMHO; This is what you would like, not what I like. Take my opinions with a grain of salt. Choose what you like, not what all of us like.