Dear Sprog, What tonearm? No surprise that you like the A90 better than your Koetsu. Apparently many others would prefer it as well. Koetsu is not my religion, but I hope you will pardon me if I say I still enjoy my Urushi and will continue to do so. (Never heard a stone-bodied Koetsu.)
I certainly would not be among those who would trash you or the A90. In fact, I own and enjoy several different cartridges and have had some thoughts about acquiring an A90 myself. But I heard an A90 in direct comparison to the new Allnic Puritas cartridge, both on the same turntable and in the same brand of tonearm. (Two arms mounted on the same tt.) I have to say that the A90 was very fine, but the Puritas was a shade less mechanical, more "musical". I hate when folks use that word as a descriptor of audio gear, but there it is.