M2 is the American National Standard Institute (ANSI) specification for “Industrial”. MS is a lower “Commercial” grade. M1 is lower yet.
M2 requires more glue and compression to fabricate than MS.
Less glue and less compression = cheaper product = inferior specifications.
Compared to the lower grade MS; the higher grade M2 is more resistant to impact, has higher shelf strength and greater screw holding power. These are important specifications contributing to a perfect surface (no white spots), minimum chip out and good edge band holding power.