I have both. I liked the looks of the M2 in pictures, then when I got one I was not immediately impressed with it. My impressions were that it was heavier than the PM2 and it was wider. Not too wide and not too heavy for my EDC, but I preferred the PM2 for those reasons. I recently moved and I used the M2 a lot during that time for cutting boxes, tape, whatever. I learned that I could flick it open with my thumb very fast, and I could close it one-handed very fast. The only problem with frequent use was that being tip-up it took me a little while to pull it out of my pocket and get it positioned for opening. I gained a lot of respect for the M2 after using it for a month. Mine is the plain version with hollow-ground blade. I didn't like the hollow-ground blade for personal reasons but I liked the rest of the knife enough that I bought one with FFG blade to keep. I intend to use the PM2 for EDC and use the M2 for more of a hard working knife.