It’s a matter of preference, but most people who have played on the Japanese KOCs usually claim they are better than the US version. They are also the players who have been playing for years and years and are used to their imported controllers, even though the localized release fixed a lot of problems with the keys that required maintenance/modding on the Japanese ones. JKOCs and USKOCs are both inferior to arcade-style controllers (ASC) though, although an ASC is completely overkill for a beginner to the series and not necessary at all, as either KOC is completely adequate because you’re going to be playing the same songs over and over and over and over again to learn.
That being said, I have a USKOC in great condition and a copy of beatmania US that’s practically never been used that I can sell ya. I have the USKOC in my possession right now, and even though the game is at my parent’s house I can get them to ship it to you as soon as you pay. How about $50 for both, plus shipping for the controller? (I can cover the cost of mailing the game, haha)