There is no short answer to this so hear goes...
You have to take into account the hardness, the included angle, and the edge geometry, plus to a certain extent, the blade finish.
One thing I do know about our 440C, 425mod, and 420hc is that we get the same basic rockwell out of each of them. 58 to 60 was the range and that was Chuck's law, never to be trifled with.
When we were using 440C the edge geometry was
a lot diferent than our Edge 2000 geometry. The comment most often heard during the 440c years was that Buck knives held a great edge, but boy was it hard to get that edge on.
Those earlier knives had an extra operation in production that we called a "flat edge". Take a look at a new 110 from back then and you can still see a faint line running the length of the edge. That edge was slightly radiused to, thus lending to the hard to resharpen comments because how do you lay a blade edge flat on a stone if the edge is not flat to begin with? Those blades were thicker through the hollow grind which made meant they could stand up to more prying, but again, made it a lot harder to resharpen as you got higher up in the blade.
VERY tough edge and tough blade for sure but our customers were telling us that wanted something
they could sharpen. Gradual changes in the blade and edge geometry took place over the years to address this need.
Off the top of my head I think we did away with the flat edge operation before we went to 425mod.
Before we changed from 425mod to 420hc, Chuck had to be convinced that we would still get our 58-60 hardness. We did numerous tests in heat treat, and backed them up on our C.A.T.R.A. machine, a device that tests several aspects of an edge, before we made the switch.
Many of our opinions on which steel is best are clouded by all the other variables that really need to be considered together. I hear someone sware that his 103 skinner from the 60's is the best knife ever and I know that if I took a 2007 Skinner, and ground the edge the same as his, it would likely perform the same. Does that mean that we should go back to the earlier geometry? Nope. It means that for that particular person, that particular combination of rockwell, geometry, angle, works best for him and his particular needs.
My opinion has always been that to a certain extent, everybody uses their knives diferently, and sharpen them diferently so they should find the knife and sharpening technique that works best for their needs. The best thing that Buck can do to help is deliver a consistant edge to begin with. That is part of what E2k was all about. We shoot for a 26 to 32 degree included angle, which our research has shown is a good all around edge. You might want a lower number for a fillet blade and a higher number for chisel. We also made the edge more visible, easier to see and lay flat on the stone. It may appear that the edge is actually higher but that illusion is due to the fact that we don't polish the burr off anymore in the final sharpening operation. To polish it would be to give it a slight radius so we now strop it off, leaving it good and flat, therefore easier to sharpen for the customer.
I hope this helps some.
In case anyone was wondering...
We changed from 440C to 425mod because we wanted to fineblank our blades. If we could fineblank them, we could get greater accuracy on our tolerances. Much more accurate than trying to mill and drill later. We could also make the blades quicker which translated into keeping our cost down, always a good thing. This is vastly diferent than saying we "went to a cheeper steel to cut costs". Remember Chuck's law, only then it was also Al Buck's law. That 425mod was a special steel the mill made for Buck, and we paid for it.
Then years later, at the mills request, we considered the change from 425mod to our current 420hc. We were the only ones that wanted 425mod and they mainly made it for us because they liked us...seriously! But 420hc was an on the shelf variety of steel and was basically the same so...Many test later, as mentioned above, and we made the switch. Again, not Buck switching to a cheeper steel, just Buck finding a better way to keep its costs down without impacting the customer. Its a win win, my employer stays in business and we continue to deliver a quality knife.