I think that a good story is a mix of both. Too happy is boring, too sad is not enjoyable, except if you are psychopath, but I'm not sure there's alot of them on DA.
Anyways. It's your story, you can do anything you want of it. You're the "game master".
Just remember this : whatever you're gonna do, all your watchers will like it, because it will be awesome, because it's made by you, and your art is awesome.