Ultimately it comes down to what does your team do best? The Falcons sure look like a hell of a lot better when they're passing than they do when they're running the ball. Houston, on the other hand, has looked way better when running than when throwing the ball (though they insist upon throwing it way too much).
Sometimes I think coaches out think themselves. If your team sucks at running the ball, then why waste downs on a futile attempt at "balance". If your team is awesome at running the ball, then run the damn ball and stop trying to be a master of everything.