The average user can tell the difference between industry standard 3V and Delta 3V pretty easily, the difference in edge stability and therefore edge retention in normal use is significant.
The industry standard heat treat uses the secondary hardening hump and goes into temper immediately after an atmosphere quench to approximately room temperature. This heat treat was developed for tool and die where minimizing dimensional changes and reducing risk of cracking and distortion were critical and the sort of fine edge stability we need in a knife application aren't commonly seen. This industry standard heat treat stabilizes retained austenite, a lot of the martensite that is formed isn't formed in the primary quench but converts in temper, and you're increasing the carbide volume fraction while reducing cohesion in the softer (weaker) over tempered matrix, all of which leads to reduced edge stability and edge retention. Delta 3V is one of the low temper tweaks whose goal is to maximize the durability of the edge by minimizing mixed structures and maximizing the strength of the matrix. This not only improves edge stability in rough use, it allows the use of a narrower edge angle and may also support the primary carbides better leading to improved abrasion resistance. This addresses the primary shortcoming with 3V, which was a crumbly mushy edge that prevented the user from being able to fully capitalize on the alloy's inherent toughness because a knife made in 3V would otherwise go dull quickly in rough use. We fixed that and it's pretty obvious to even a casual user.
Less obvious is the difference between some of the better low temp tweaks and Delta 3V. To see this clearly you need better controls than just casual use. But with controlled edge geometry and cut media it is clear and repeatable.
There are a couple things that may be happening with those two well known smiths who tested forged vs stock removal. One could easily be bias, intentional or not, towards the outcome they wanted. To minimize this when I was first starting out with low temperature tweaks I would do blind controlled tests where I didn't know which was which until after the test. The other thing that could be happening in their evaluation is they may have seen a difference and misunderstood the meaning of it. This could be uncontrolled variables coming up such as unintentional differences in heat treat, a burned edge during sharpening, differences in the cut media they used, weaknesses in the criteria they used to evaluate the sharpness or durability of the test pieces or even differences in the materials being cut. But I think the most likely reason may be the forged blade legitimately out performed the stock removal blade. Not because it was hit with a hammer, but because of the multiple heats it was subjected to during the forging process that the stock removal blade didn't get. The forged blade would have gone into the heat treat as a fine homogenous pearlite while the stock removal blade may have been in a coarse sphereoidized condition (as it comes from the mill). Had the stock removal blade gone through the same thermal cycles as the forged blade it may have been a different story. If those two smiths saw two identical blades in the same steel at the same hardness perform differently I believe them because I've seen the same thing myself. And if they misunderstood the underlying reason (forging rather than thermal cycles) they would only be human, and I can relate.
My methodology that we used when developing the Delta protocol was a skill set I developed working in product design and development where we would optimize a product's characteristics and manufacturing processes through an iterative process similar to what you experience when you go to the optometrist for an eyeglasses prescription. You develop a matrix of variables and a testing procedure to evaluate the effect of changes to those variables and compare work while also attempting to track relationships between the variables because of complex if/then interactions. Much like natural evolution you dial in an optimized process. You can have working theories about why something works, but an important distinction between science and engineering is the emphasis on optimizing an outcome more than necessarily understanding the underlying reasons. So, while we don't have an SEM in the shop, we do have the ability to control variables and measure outcomes. I can say with complete confidence that the difference between industry standard and well optimized low temper tweaks like the Delta protocol is very significant and difference between Delta and the low temp tweak that immediately preceded it is meaningful.
A casual user can see this. If they are a real user. Obviously the difference isn't noticeable to a collector who only occasionally cuts a piece of paper or string. I'm a pretty bad abuser of knives. Yesterday I used my knife to deburr a thread in a steel part I'd just cut. I used a piece of steel as a cutting board to cleanly cut some o-ring cord stock for a gasket I was making. I shaved steel fines out of an aluminum fixture. I do all of these abusive things with a knife with a narrow edge angle and I like my knife to be sharp so I can still cut the cap off my cigar without messing it up. The difference in edge stability between an optimized heat treat and a average heat treat can be a HUGE difference in sharpness at the end of the day. So if you're a guy who might clink his knife against a beer bottle when opening a case of beer, or bump a steel staple when opening a box, or cut wire and deburr hard objects you will notice the difference. If you only cut the occasional loose string you probably won't, but it's still nice to know that you can.
A Carothers Performance Knife in Delta 3V will be sharper than another industry standard 3V knife at the end of rigorous use such as weekend hiking trip or a week of use with a tradesman etc. And the thinner edge geometry cuts better too. Ask anyone who uses them.
Alchemy1 basically summed up my thoughts much more succinctly than I did, while I was typing my post.
