I’m very late to this discussion. For what it is worth:
I’ve used Koetsu almost exclusively for 40 years.
the Black for 20
the rosewood signature for 8
the non platinum onyx for 12
for 15 months, I’ve had a Leopard platinum. I’d rotate it with the onyx while it was breaking in. The Leopard was faster, had better bass. The onyx did everything else better. Then, during the last two weeks, after 350 hours of break in, the Leopard suddenly took off and is quite improved over the non platinum onyx in about every way.