Sony & MTV are calling it Rock Band Unplugged Lite, because (this is the stuff we didn't already know) while it'll begin its life as a singleplayer demo (with 5 songs), it'll also be compatible with any DLC you may wish to purchase from the PlayStation Store, making it far more useful in the long run.
Except...you have to pay for those extra songs. Europe's Gran Turismo deal is just...Gran Turismo. You buy the PSPgo, you get the full game. Not hard seeing who's got the better deal here.