L4U is all stage performances. However you have more free reign in selecting what songs you want to play, who you want in the performance, what you want them to wear, etc. then in the regular game. It's a lot easier to understand and play if you don't know Japanese too.
If you get the regular game, it plays more like well...a game haha. So if you're expecting to watch your idol sing and dance, you have to work toward it with lessons, communications, etc. It's a bit tough to figure out at first, but after multiple playthroughs, you end up knowing what to do.