On paper, M-2 will have higher wear resistance and will thus be expected to hold an edge longer. A lot depends on how the M-2 is heat treated though, and on the edge geometry and materials that the knife is used to cut, not to mention the corrosiveness of the environment.
If you are speaking specifically of Benchmade's M-2, as found on the Nimravus, compared to VG-10 found on a Fallkniven F-1, then I would go with the Nimravus for edge holding. I have not hade much experience with VG-10, but based on what I have read of the Fallkniven blades, VG-10 is a good tough stainless, but not the equal of a high speed tool steel in wear resistance.
But again, the difference would vary greatly depending on how the knives were sharpened and on how much salt and water they worked in.