Just my thoughts - I heard 3 different Corals in 3 different systems, including on a Kuzma and an Ikeda, and did not like any of them at all. I also heard 2 RSPs, or RSP sigs, on SME 3012r and Reed and did not like them at all (Reed was ok, just another cart). They were also compared to other MCs they lost out brutally to
So, I was pretty disenchanted with Koetsu. In fact, I recently even texted Gian that the SPU a95 would be better than Koetsu for same goals - good body and flow, at the expense of some highs and details - at a lower price.
However, when I heard Koetsu Black upwards at Shakti's I realized that all those previous demos, I had not heard the Koetsu at all
When Ron texted me to ask how Koetsu compares to Zyx on highs, mids, and lows, I replied that I think Koetsu will lose out to all if you do an attribute by attribute comparison on highs, speed, detail, transparency, etc...however, what Shakti and I heard, and what 853guy seems to have emphasized too, and what Tang mentioned above, is the integrated whole. It needs to produce that front to back, side to side, dense integrated whole, where the highs, details, and speed are almost as good as your other MC cart - the highs, details, and speed will not be more but they will not less enough to make you reject the Koetsu, they will be there while you focus on the positive aspects of the Koetsu. This is what Shakti did with the titanium headshell on the FR, increasing details and highs to be sufficient.
As such, I do not think it is a cart for mids and vocals, but for that integrated whole, the flow, the density, the body, and the involvement. Actually, I like my vocals to be clear and transparent and soaring in the highs with good midbass chest. Examples of two compares, I preferred the highs of the Bernings to the Vitus on vocals, though I preferred the midbass fullness of the Vitus on the baritone. I preferred that Spectral made it seem the singer's mouth was wide open, as compared to the VTL which made it sound as if the singer's mouth was half shut (though had better harmonics). On the YG, the Winterreise Leider vocals sounded better on the colibri.
Another point - a Koetsu did come across as lethargic to me previously, but not so in an FR which seems to handle that energy well, possibly because of the lack of damping as Shakti described.
On Tang's reference to Mike's GFS and vocals, I think those vocals were just perfect - completely organic, magical, and well positioned and coming from the deep stage. Probably a combo of the arm and the cart again. But it is unfair to bring that system in because it is not a system for tradeoffs, it just excels on all attributes. I would be skeptical if a Koetsu would do well in his system unless he sets it up in some special way to tune in to the rest of his system, but then analog keeps surprising