The structure I've seen more often, especially in action/adventure fantasy, is that the choice comes *before* the climax. It's the choice that causes the final confrontation. The climax itself is discovering how that choice works out. Like, they finally choose to fight, and then the battle itself is the climax, but it comes after the choice.
Of course, there could be morally charged choices at the very end too. But I don't think this is necessary for a strong conclusion. I've seen too many attempts where it ended up sounding contrived. So, if it arises naturally, I would go with it. But I would never force some choice into the very end if it's not a natural out-growth of the events up to that point.
As for my own books, I currently have one of each type that I'm completing. The Nano characters choose to finally embrace the darkness right at the end, while the characters in my other book made the choice to start the revolution way back in chapter 16 and spend the last four chapters making it happen. They don't have a lot of control left by the end, really, because they've started something much bigger than themselves.