I asked a question like this on Ask Metafilter[0] and got some detailed answers. The consensus among metallurgists, rather than swordmakers, is apparently that almost everyone had crap iron to work with, and various techniques for dealing with that; but Japanese process was better overall because the rarity/expense of iron in Japan meant more effort (expense) put into labour. It was easier to get a cheap, crappy blade in Europe.

[0] https://ask.metafilter.com/153280/Steel-is-strong-but-flesh-...