As was explained in a lengthy discussion here some months back, which included the expert input from an APEX employee who designed the APEX barrels for the M&P, there is a slight functional (not cosmetic) difference between the 1.0 and 2.0 9mm slides.

Some extra material was added to the 2.0 slide by S&W to prevent some very subtle STRETCHING of the slide while the round was going down the barrel. That stretching affected accuracy. The larger caliber slides did not have the same problem, as they were a bit more robust.

Aren't there some slight/subtle changes in the slides where the slide stop is located? (I only have a 1.0 M&P Pro.)