How brittle M2 will be in use depends on how it is heat treated. If it is left at full hardness ~65-66 HRC, then you could likely chip it out very easily. However it is usually ran much softer, ~60 HRC, and assuming similar edge angles to the above mentioned 1095 blade, you would need to bash it into a rock or similar to chip it, of course at that level of hardness you get little benefit over just running 1095 anyway.
The big problem with ourdoor blades is repeated shocks, M2 was never designed to take these kinds of impacts nor extensive bending, and thus is a poor steel for those kinds of tasks, so are steels like S30V and S60V of course. For that kind of pounding and bending you are looking more towards the spring and impact steels.
As for edge retention, what dominates in most light cutting is just hardness, as all you are seeing is the edge rolling. There are some materials which create wear, thus M2 would outperform 1095 at a similar hardness, but on those materials such as gritty rope, you also get more complicated dependance because now toughness comes into play as the edge can chip and simply bend fracture instead of wearing and rolling.
The heat resistance is an interesting issue because even cutting normal materials the edges on knives can heat up well past the point were they will readily burn human skin on immediate contact. This is the same point that knifemakers warn about when grinding knives after heat treating, as various tools steels are often tempered at very low heats.
-Cliff
