Currently Have:
Koetsu Onyx Platinum, Jade Platinum, RSP, and Onyx Signature (1990s, needs re-tip)
Ortofon Cadenza Bronze
Ortofon MC20 (not mounted for quite a while now)
Have Owned (but sold before I upgraded to my current Clearaudio Innovation Wood & Graham Phantom):
Ortofon Windfeld MC, Jubilee, Kontrapunkt "a" and "c"
Benz Ref 3, Wood M2, Glider L2
Obviously I love the Koetsu midrange. It's organic, and silky smooth. For vocals and strings in particular, it imparts a lifelike presence and energy. Also, depth of image is the best I've yet heard; very 3D. Treble/resolution/speed are very good but not as good as the MC Windfeld. Bass is good but even further from the likes of the Windfeld (which frankly has amazing bass response). But then the Windfeld has a very thin, dry, perhaps even soul-less midrange compared to Koetsu. Also I had a bit of a brightness peak problem with the Windfeld that made it difficult for me to enjoy consistently; maybe this would be mitigated (or outright solved) in the new setup. Overall, my memory of the Windfeld was that it was very fast and resolving, with epic bass (power, quality, and extension) -- and a clear step up from the Jubliee (which I did NOT prefer over the Kontrapunkt "c").
Now I have the Cadenza Bronze, which like its predecessor Kontrapunkt "c" has a midrange more to my liking -- though honestly I remember the Kontra "c" having slightly fatter, lusher mids (still not into Koetsu-territory mids, though). I like that the Bronze has what I consider a neutral tone -- not bright nor dark -- similar to how I feel about the Koetsu Platinums. I also like that the Bronze features more powerful bass than the Koetsus, though obviously not to the Windfeld's level of excellence. From memory, the Bronze is a bit cleaner in bass an more resolving than its predecessor Kontra "c", but again not to Windfeld levels -- and not quite to the Koetsu level either.
Switching from the Bronze to a Koetsu Stone/Platinum makes for a striking contrast (relatively quick and repeatable thanks to 2 arm-wands). Going to the Bronze, I dearly miss the Koetsu mids and refinement, and going to the Koetsu, I really miss the Ortofon bass and the way it anchors the music. That said, Bronze mids and Koetsu bass are still quite good when NOT directly contrasted to their superiors, so I've learned to pick 1 cart for a session and stick with it till the end.
As far as the Koetsus go, the differences between the Jade/Onyx Platinums are almost negligible. Some slight slight differences that are hard to explain and may as well be due to natural variations from the manufacturing process. They both have a little bit better bass response than the RSP, but all 3 are otherwise extremely similar. The old Onyx is even MORE Koetsu in the midrange and stage depth (really beautiful sounding), but not as resolving nor extended, and the bass has a bit more oomph but is not quite as clean. A bit on the warm side, and an interesting cart for sure. Though this one needs a re-tip, unfortunately.
Part of me wants to give the Windfeld another shot, but I'm not sure if that's the right move in light of my love for a rich midrange -- or whether I should remain content with the Bronze.