Hey guys, I've been looking at Semi-auto shotguns. Can someone be kind enough to enlighten me on the difference between the Benelli M1, M2, M3, and M4? They seem to get more expensive as you go from M1 up to M4. I've been on the Benelli website, but it doesn't really say much about the differences. I have noticed the M3 is 'convertible', meaning it can be used in semi or pump mode (if I understand correctly). I want it for home defense. It might go hog hunting some day.....but right now, I'm looking at it for home defense only. Thanks in advance.