I made the comparison 2012 with the recent IT-407 model. I can't say anything about quality differences....but who knows. Gordon Holt (founder of Stereophile) said a remarkable sentence in an Interview some few years ago:
The 66s was outstanding expensive, sold in low numbers compared to other Arms and even after 20 years it is hard to get one and when someone looks for a full Box, he has to pay thousands of $ in auctions. That Arm (and the FR-64s) passed the test of time.
J. Gordon Holt 2007
No audio product has ever succeeded because it was better, only because it was cheaper, smaller, or easier to use.
The 66s was outstanding expensive, sold in low numbers compared to other Arms and even after 20 years it is hard to get one and when someone looks for a full Box, he has to pay thousands of $ in auctions. That Arm (and the FR-64s) passed the test of time.