Price, which is reflected in the materials, machining ( tighter tolerances) and finish. I have a 3020 and a M300, both of which are serviceable and proven killers. I also have an SA-28 which is my primary gun right now. All that said, I just ordered a SBE3 28 gauge with a 26" barrel ( shortest I could get ) and am going to try an IC, Sumtoy and probably a Jebs choke to get the best performance out of it. Sorry for the ramble, lol. I would go with the m-2 with those choices. If they had a 28 m-2, I would probably be going with that. Z