Saying that one steel is harder than another or "holds an edge better" is a serious case of oversimplification. A 1095 blade at 60HRC is harder than a D2 blade at 59HRC. In this particular case, I think the range listed for the D2 is 59-60HRC and 57-59 for the 1095, but that's a manufacturing choice, not an inherent property of the alloys.
Now, D2 has higher abrasion resistance than 1095, which affects its ease of sharpening and reprofiling, but not to the degree that so many claim, especially not in the era when you can go to a hardware store and plunk down $17.00 for a course or medium DMT. The higher abrasion resistance is often touted as a boon to edge holding, but this is really only true in specific types of cutting. Most dulling that people experience during knife use is not abrasive, meaning not that the steel is actually getting worn away. If you're going to be slicing extensive amounts of cardboard, rope, or other such abrasive media like furry animal hide, then yes, high abrasion resistance is going to be an aid to you. Most people don't do that type of extensive cutting with a seven inch long, saber-ground blade however.
The principle difference you will see between D2 and 1095 Kabars in terms of edge holding lay in their behaviors under different types of stress. Most dulling, especially in this type of knife, is not from the steel getting worn away but from edge damage in the form of deformation or fracture. Both steels will do both, but 1095 leans more towards deformation while D2 is more likely to fracture. D2 has higher deformation resistance than 1095, so it is less likely or "willing" to roll/dent/blunt, and so can support a thinner edge for extensive push cutting and shearing (think paper cutter, planing wood or batoning). On the other hand, deforming isn't all bad, as a rolled edge can be straightened. D2's edge loss is more likely to take the form of edge chipping--the low ductility of the steel making it less capable of hanging together once its strength has been overcome. Fixing a chip generally means filing/grinding away a lot of good blade material surrounding it.
So, for some cutting applications, D2 has better edge holding than 1095. For some others, 1095 is better. Don't buy the line from anybody that any cutlery steel does EVERYTHING better than another, that's simply not the way materials work. Focus on making an alloy exceptional in one area, and it becomes less exceptional in another.
If you're planning to do a lot of chopping/hacking with your knife, D2 is not a step up from 1095--you want added ductility in a blade that's going to see a lot of impact use. If what you're doing is going to be more general cutting, overall it's got a bit of an advantage compared to 1095. While I have to give the requisite "...a knife is the most expensive and least effective prybar you'll ever find" line, the deformation resistance of the two is again a factor--the D2 blade, especially in this case where it's probably a point or two higher on the HRC scale, will take more force to bend. However, it's also more likely to break when the strength of the blade has been overcome, where the 1095 will generally flex more without damage.
Of course, if you're going to be in very wet conditions, that affects edge holding too. D2 is right on the brink of being considered stainless based on its chromium content. It will rust (as will 440A--there is no truly "stainless" steel), but resists it much better than 1095 which has just about zero corrosion resistance. Just humid air will dull a knife edge over time, oxidizing that thin strip of steel and weakening it.
But, some points of practical realism--these differences are detectable between these alloys, but all of them are steel. D2 will not shatter at the drop of a pin, 1095 will chip and, as mentioned, 440A will rust. None of them simply 'holds an edge' better than the others--it depends on the use and conditions. You make gains and sacrifices no matter which way you go.
As to the higher cost of the D2 extremes, part of it is reflective of Kabar's initial cost of bringing these out several years ago. They required molds to make the handles, new materials, new tooling and different heat treatment procedures. Also, especially back then, D2 was definitely a buzz steel to the production knife industry and the demand for knives in it played into their pricing too. True, the molds and tooling have long been payed for, but once a price point has been accepted, manufacturers will tend to stick close to it, or at least not drop it down much--just the same as any industry. But yes, D2's added abrasion resistance does mean that it wears out machines/wheels/belts more quickly, and takes longer to work with.
As to whether it's worth it to you, you have to make your own judgement call on that based on your typical uses for this type of knife, level of sharpening skill (although again I HIGHLY recommend getting some good quality diamond sharpeners--they're less expensive and more rugged than ceramic sharpeners and diamond really isn't impressed with the hardness of any steel), and how interested you are in experimenting with different blade materials. I really like D2, really like 1095, and if I'm fishing saltwater or cutting up a bunch of vegetables, I really like 440A.
Best of luck,
Warren
