Crag the Brewer
I agree that deliberate side by side comparisons would be great, and I definitely wanted to do so. But between work, a toddler at home and the FYE season, my time was limited.
However, without a doubt I can say that my EDChef XL in 15N20 has superior edge retention. The EDChef is extremely thin behind the edge, with only a small bevel on the cutting edge. I use this knife every day, usually multiple times a day, to cut the same food stuffs (often thicker, tougher things like bones, butternut squash, etc.) and on the same cutting boards I used with the M2 mule.
The EDChef consistently cuts through tomatoes with one slice while only requiring a touch up once a week on my diamond hone and butcher's steel, with occasional passes on the steel 1-2 times per week. Whereas the M2 mule required touch ups on the diamond hone at least once per day between meals, and sometimes more than once.
I tend to rank my 52100, 15N20 and O1 knives in the same general caliber regarding edge retention. From my experience M2 is significantly lower on the totem pole than those three.
It is worth mentioning that these comparisons are based on the premise of how long the steel keeps its screaming sharp edge during normal use. In that case M2 loses rather quickly compared to the three steels above, but is able to hold its own with a decent working edge for a long time after losing its crispness. I don't hold the cardboard cutting tests too hard against any carbon steel since few of them really excel at it (if anything, the M2 might have an edge there since it can be kept thin without sacrificing too much toughness).
