I'm not talking about the potential of the various steels, I'm talking about what we see in the end result.
If I have a chisel with voids in it, I'm not really interested in what it would look like if it could potentially not have voids. I'm more interested in what we see when examining finished tools.
So, if the japanese steelmakers deliver steel that can be pretty much cut and heat treated and that looks like this as it wears (these are blue, #1 or #2, I'm not sure - I've seen them sold as both, but I doubt tsune makes more than one type):
Or they can make relatively low priced chisels (iyoroi) that don't get much special attention other than a quick smash by a power hammer and run through some grinding dies, that make a difference at ground level.
If Austrian O1 steel was used, and of the highest quality, for western tools, the issues for O1 would be different, but it doesn't appear that that's the case.
(other references for visuals to compare against the Tsune)
LN A-2- http://www3.telus.net/BrentBeach/Sharpen/LNA2test.html (there is a gigantic difference in using an iron like this to smooth vs. the tsune - the tsune will still provide a line-free cut all the way until it stops)
LV A-2 http://www3.telus.net/BrentBeach/Sharpen/LVA2test.html
( I didn't test an A2 blade from LV about a decade ago when I stroke tested IBC vs. LN, at least I don't recall it. I don't remember feeling like an LV A2 iron was lacking, but recall that they weren't cryo treated at one pint)
And for comparison to those:
Hock O1: http://www3.telus.net/BrentBeach/Sharpen/Hocktest.html
Note that the berg is a couple of clicks softer than the hock, and it might be slightly different in alloy if it uses swedish ore.
I always felt the hock iron was too hard to be good. Ron disagrees with that and states that you ruin his iron if you temper to straw. I have since made my own O1 iron out of starrett O1 stock and tempered it too light/medium straw. It holds up better than Ron's. George has since stated the same thing, that the Hock irons are too hard to hold up well for A2.
To quote Hillary, what difference does it make? Well, I tossed my O1 irons when I had only hock O1 and went to the hock A2 (which holds up about as well as LNs) because I had a single plane that I was using both in at the time. There was a marked difference between the two in use. If the hock O1 went a distance of 3, it chipped early and the A2 would go 5. Pick your favorite unit. I was flattening panels with both, so I could go through a whole sharpening cycle on same wood same size. The tsunesaburo and a subsequent shark iron (something from esikilstuna) would last about the same as A2. My O1 iron is close but not quite up to that level, but lasts longer than the hock and doesn't have bad surface quality.
So, noting the difference in all of these rikizai tools and wonderful low-priced kitchen knives that are light and a dream to use and that hold an edge very well, and the expensive hand forged tools and irons? Not much until you start doing bad things. For example, take a $30 violin knife made of rikizai and try to trim an iron ring on a japanese chisel. The result is bad. Take a plain carbon steel knife or chisel made by someone who is known for their forging skills and you can cut iron with carbon steel.
In use with wood, there is probably a noticeable difference between the two, but it's relatively small. In terms of the rikizai tsune iron, I can't imagine a forged iron would do much better. Rikizai's limitation is generally toughness, but the iron shown on beach's page lacks nothing. The one I had also lacked nothing and never failed by chipping. When you sharpen it, it holds almost no wire edge. It's just better.
If western makers would be willing to offer it and follow the same schedule that tsune does, they'd have something wonderful. Tsune's irons are fantastically thin (but still fine with the cap iron, they'll stop you in your tracks). Catalog buyers wouldn't be able to get over the thinness, so something a little thicker would be needed. Deba (thick) are made with rikizai, so I'm sure something suitable could be found.
(the discussion above with rikizai may not be as true when you're trying to squeeze all you can out of a kanna -there may be a critical angle where it falls apart and hand forged stuff does not).