I Beacon's brother, will be playing with him and my roommate in some versus.
The big question with SE is how many choices do you make, and do they have any true impact on the story.
For example, let's take the one we know. Save Peach or Zelda. It's very possible that your next mission will be Kirby + X and you rescue Y, and then the next mission you play as Peach and Zelda and it has no impact on the actual story.
Or it could be that rescuing Peach will cause a different chain of events where Link shows up, which in turn gets him seperated and he joins up with Yoshi while chasing Wario through the plains. But if you rescue Zelda you chase after Wario with Peach, and instead of Link, Luigi shows up, causing Wario to go down a different way. Luigi chases after them being aided by... let's say Snake. Each of these leads to a second choice, which gives a total of four different outcomes. And so on.
I'm hoping it's the latter for replay value, but that's a lot more work, so I won't be surprised if you have no impact on the story line other than a couple of "who you're playing with"
I'm thinking it's the former as if it affected the storyline too much, it's one...too much work. You'll have to play the game again and again to be able to reach a desired alternate ending. Second of all, that'll be too hard to make as well. I think it's impractical for the staff to make various endings for a 10+ hour game.