the m2 is just the newer version of the m1. It has a couple of new features like the "chrio tech", "air touch" and "comfort tech" besides that i think the guts are about the same, same recoil ejection, no gas tubes or o rings to go out on you. I've got the M1 and love it, in 8 years never had a shell jam on me. Either way you go you're set. they are great guns. if you have any other questions feel free to pm me
Joel
