In the first and second SC, I'd shoot them all if possible. In CT and DA, I knock just about all of them. Cheap-ass way to finish, but it leaves a 0% chance of being detected on your way out.
I like to grab them from behind in CT, since they all have unique things to say to you and some of their comments are quite amusing. They took a step backwards in DA and made it like the previous games, where only a handful of guys would say anything to you.
As for the music, the SC games have generally had very good music. It's dynamic like FS2 and changes depending on the situation. That was the one thing DA actually got right, as the music is not only excellent but also implemented well. As I mentioned in the first post, the music volume varies depending on how close you are to an enemy, which adds to the tension when you're trying to creep up behind someone.