Personally, I like Justin Willis. I don't claim to be a coach, and therefore I am not qualified to declare who should or shouldn't start.
However, from the little I've seen when I have stopped by practice, Willis might have the least arm strength of the five. It's not a weak arm, by any means - we all have seen him hit some deep passes for touchdowns over hte last couple of years - but I wonder if he can throw the deep out route that Coach Jones seems to have liked in Hawaii. That's the route Troy Aikman once said got him in the Hall of Fame, because he could snap the ball to the sideline 15 or 20 yards downfield.
Maybe I'm way off base here, but I wonder, while Jones has said accuracy is most important, how raw arm strength factors into the equation. We'll see.