Clubs with Japanese spec usually have a swing weight of 1 to 2 points less than US spec clubs. Also the overall club weight can be a little lighter, which makes them a little easier to hit for the novice. Also the shafts are a little softer in flex. Japanese spec clubs tend to be a little more expensive compared to US versions.
I used to use US spec clubs with steel shafts (Dynamic Gold S200) for the longest time but as I am older have switched to softer Japanese NS Pro steel shafts and have regained the flight trajectory and distance that I used to have. So it all boils down to knowing what to buy that will fit you.