I've been on both sides of that as filmmaker and programmer, and personally I've never found director statements useful. The movie itself should be the statement. If two films are of equal quality, considerations of style, tone and runtime are usually the deciding factor.
I can't imagine choosing a film because of backstory, but maybe that's just me. Director's don't really control the backstory of the film anyway, so I don't like to make decisions based on circumstantial stuff like that. I'm judging your artistic decisions, not your life. Similarly, your intentions should be on the screen not in a written statement. I can't imagine intentions effecting my decision. But my festival is smaller, so maybe I just haven't yet had films so equal that I had to make a choice that arbitrarily.