hum...i think that in this saya no uta heavily contrast with, say, chaos;head. I like both a lot.
But there's just one true ending in chaos;head, but there's a lot of options. They would either:
-go into the delusion system. This is, you will either see the real (neutral) scenes, or a violent variation (in case, the protagonist is the one that suffer) or a sensual variation. No impact at all in the endings. It's a very "sandbox aproach".
-go or avoid death endings.
Then we look at saya no uta. There's just 2 questions in the whole game. They will directly determinate the routes and the ending that you can get. This does means that it's less interactive...you won't be able to take actions in the rest of the history. But when you do take a action, it have really really heavy implicances in the course.
Giving a example of this in rpgs: tactics ogre battle: let us cling together (psp).
At the beggining, you will be asked a sequence of questions in moral dilemas. There aren't correct or incorrect answers.
It will affect the status and attacks of your "Hero", that you will be obligated to use in every mission and the class can't be changed.
When you advance more, you will be confronted with moral dilemas, around lawfull and chaotic options too. Its the D&D definition: lawfull following duty and responsibility (what sometimes can obligate them to commit bad deeds), while chaotic are the free willed (what put all the responsability in them about deciding what is a good or bad deed). Again there's no right or wrong. But it will drastically affect the route the story take, and what characters will wan't to fight under your command.