Crossbow or Longbow? What's Better for Defending Your Medieval Tower?

When you are hanging out in your medieval tower and get besieged, do you reach for a crossbow or a longbow? In the hands of skilled archers which will allow you to shoot closer to the base of the tower?

And of course the opposite is true; how close should you get to be safe from overhead archers?

Joe Gibbs is back shooting his 140lbs longbow and Tod is back (well I am always here to be fair), shooting his 860lbs crossbow off the battlements of Harcourt House.