If Japanese clubs were better wouldn't you see one or two of them on tour??
Almost EVERY forged iron you see on tour is Japanese. The clubmakers have a select number of Japanese forging houses make the tour irons. In fact, when you see most tour Taylor Made R7 TPs, they are forged, and forged in Japan. The R7 TPs you can buy in the US are cast.
The Titleist forged irons tour players use are Endos. So are ALL the Callaway tour irons. Tiger's Nikes are Miuras. If you want Tiger's irons, you can get them in the Miura name for a cool $10,000. The MacGregors are Miuras too. There are a few smaller forging houses in Japan that make some of the other irons on Tour too.
Srixon does their own forgings as does Mizuno. If you buy Japanese market Srixons or Mizunos, they are higher quality and newer designs than what's sold in the West.
Almost all the rest of the forged irons in the US and Europe are Chinese forgings. A notable exception is cast clubs. Those are pretty much the same heads, but totally blueprinted for the player to his specs.
Someone asked about blueprinting. The tolerances on clubsand shafts are very broad. Most drivers have a lot more loft than stamped on them, most irons have lofts that are not accurate, the lies are not accurate and the shafts will vary widely in frequency (the measure of stiffness). Why? In order to meet market pressures, they are slapped together in China by people who are low paid assembly line workers and usually know nothing about golf or clubs. A noted exception is Ping. Their Tour clubs are the same thing we can buy, but of course they are cast and their irons are made in the US.
A great example is my friend Doug. Doug bought a set of $1000 irons made by one of the big names. They had Project X shafts too.
When they were checked, his lofts were way off, his lies varied from 2 degrees flatter than spec to 2 degrees more upright than spec. All in the same set! His shafts were supposed to be 5.5 (stiff). They ranged from 4.0 (ladies flex), through over 7.0 (XX stiff). All in the same set. He got them blueprinted. He immediately scored about 5 shots better per round. He paid HotStix $400 for the fitting and then bought new clubs from them. Total bill was $2,800 including Driver, 3 wood, hybrid and irons.
This lack of quality control has created a new type of equipment specialist- the blueprinter. Probably the most famous is HotStix, but there are many others. They take your clubs, fit you properly, then bend your loft and lie to your specs. They check your shafts for stiffness and repair or replace any shaft that is out of your proper spec. Usually they will also spine them. It's a lot of work. All tour sets are built this way.