Thinking of getting a shotgun soon. Most likely a Mossberg. I know the primary differences between a 590A1 and a 500 are that the 590A1 was built for military duty (Thicker barrel walls, metal triger gaurd and safety). I didn't know if I needed the heavy duty barrel, and I know I can replace the trigger gaurd and safety on the cheap. So is there a real advantage to getting the 590A1. There seems to be a pretty big price difference.