Uh, how they play it is very much the same thing, except for experience point party style, and that is mostly cursory differences. JP like to sub white mage to corsair while NA sub ranger, and tend to end parties at a set time rather than get replacements. Their DD classes tend to sub ninja for protection even when DoT could be raised safely by subbing SAM or WAR. They tend to be a little less hardcore than NA, which is why it was a NA shell that first fought pandy warden. They also tend to be more insular, and uncomfortable with western parties, either due to language barriers or xenophobia.

Other than that there really isn't that much difference, because FFXI is a very linear game. They do nyzul isle the same way we do, they do endgame the same, they mostly play jobs the same way and are affected by nerfs and buffs the same. There really is little regional difference in how to play the game in terms of mechanics.

If you don't believe me, Elmer the Pointy writes a great blog at http://www.jpbutton.com in which he writes about the japanese aspect of FFXI, and he often translates and shows SE news and japanese player info.