Ask yourself what is the most important attribute of the knife. From your post, lets assume its toughness, with edgeholding a close second. From that list, S7 is the one I'd go with. Ridiculous toughness at relatively high hardness, 55-57 HRc. Edge holding will be lower than any of the others listed, unless the edge is dulling because of chipping, whether the chips are visible to the unaided eye or not. If edge holding is farther down on your priorities, say toughness is 10 and edgeholding is 6-7, instead of 8-9, you can get tougher steels such as 4140 and 4340. Keep in mind these are not cutlery steels and are typically not put into service with hardnesses above 50 HRc. Of course, their service rarely includes cutting. Some makers use them for tomahawks and hatchets, but no knives I've seen. If any of the makers use it, L6 tool steel is a very tough steel and will reach hardnesses greater than S7 can, therefore holding an edge longer while still having adequate toughness. The plain carbon steels are also quite tough as long as the carbon content is kept relatively low, such as 1055, 1060, and 1075. Dont forget 5160 spring steel, 9260 silicon spring steel, A8 air hardening tool steel, 8670M spring steel, and CPM 3V and S5 tool steels if you can find them. These all have a reputation for toughness, with edge holding that is adequate to excellent.
If edge holding is equal to toughness, then 52100 and possibly A2 are good choices. I would stay away from the D2 and S125V unless you have experience with them already and know they can handle what you want. And of course if toughness is king and edgeholding is out the window, there's good old 1018 or A-36, both of which are soft enough that you practically have to tear them instead of break them for knife applications, but will bend if you hit anything more substantial than a 2" pine tree. I'm getting long winded in my old age. I hope that wasnt too much to take in.
