From the research that I have done on line, this web site, and over the phone, from what I am hearing it sounds as if there is a big difference in terms of noise, as well as quality of the motor. Not having heard these motors b/f and, unfortunately, I have no starting point on how to judge how quiet the american motor is -- this is going in my living room. It could be that the japanese motor is just really quiet where as the american motor is quiet.
Not sure if I am going the Japanese direction, just want to become as educated as possible b/f I make a decesion b/c it is a lot of money for a pump and from my understanding is that Iwakis last a long time and if you break down the dollar difference over the number of years that I will have it, it breaks down to almose nothing.