In order of the quality of edge steel after adjusting for variability:
japanese white 2 (and other similar mid-level steels that the japanese use in commodity tools) > good vintage steel > modern process steel of reasonable quality > (tied for last is two - bad vintage and bad modern process)
Cue Itchy and scratchy theme music with the topic..."fight, fight, fight.... fight, fight, fight...."
I took some pictures with the microscope earlier this month (last month?) to flesh out really perfecting sharpening razors and identifying dud razors (some don't hold an edge as well as others, and when the angle is 16-18 degrees, mediocre stuff is found quickly.
One of the things that i noticed is that at a true level of about 150x or so, I could see all sorts of voids in a set of ashley iles chisels. These are obviously modern process steel (I bought them last year). I wasn't looking at chisel steel, I was looking at what the various stones do to steel of different hardness to see if I could prove what's generally well known - that harder steels will take a better edge off of a given stone because the grooves aren't as deep.
Anyway, this is a picture of the Iles chisel. This was actually one of the better sections. I didn't want to show the sections that had bubbles right at the edge because they looked terrible due to the magnification, but are not visible to the naked eye or look like tiny flaws (the edge just looks uniformly polished otherwise). Even in this relatively clear section of chisel, there was still a bubble at the edge and you could see other small voids.
I bring this up, because on another forum, we often see criticism of old steel and discussion of the superiority of modern steel because based on reading books about steel process, etc. I've never thought the new steel in western tools was better than the better old stuff, for more than one reason, but the assumption by new process proponents is that all newer steel is defect free or close to it because of modern process controls.
I am going to look at more old irons (I probably have 75 from various makers on the doomsday scenario that I lock myself in the garage and attempt too make a whole bunch of planes in a row at some point). And perhaps more japanese stuff.
My supposition from use is that once you discard the 5-10% of older stuff that's just not that great, the rest is at least as good as modern and some better.
Modern steel is uniform, and often defect free, but no better than the better vintage stuff (in edge holding, etc).
And generally, white 2 japanese steel is better than both. As much as I like vintage steel, it's not as good as yasuki (hitachi) white 2 and probably nothing is more consistent. I use white 2 for two reasons- it's apparently not that hard to heat treat properly (white 1 is a different story), and because it's out there in droves in tools that don't cost that much.
As for the iles chisels? the bubbles or voids are ugly, but they really don't make a difference in day to day work because they are so small. I like the chisels plenty enough that I just don't care. And those chisels like natural stones and have reasonable hardness, which is another bonus - they don't make a huge ratty wire edge that they don't want to let go of.
Razors are a different thing entirely, but interesting with them, the razors made in the 1800s aren't really that great. I don't know why that is. Of course you can shave with them, but the cutlers didn't perfect the grinding, heat treating and finishing process until later on. Maybe 1900s, and perhaps a little after that. The difference in result is not one that would matter much for woodworking tools, but when you put the edge on your face and shave with a razor for a month, it's definitely noticeable (a good razor will start sharper and stay sharp longer, all other things being equal - like hardness, etc).