In a previous post I dared to compare them, since I own (and listen to) both. This was the summary (IMHO, obviously):
CHARYBDIS: enormously resolute, without falling into tonal imbalance; details at the tip of the iceberg that, however, are not thrown in your face; they translate dynamic contrasts without problem; they attack until they bite, although without making us bleed; crisp and forceful bass; textures of the first level; very good separation and air, but at the price, which we can gladly pay, of placing us in the first row.
CALDERA: "neutral" profile, tending to warm, but with more than enough resolution; smooth treble; dynamic contrasts... pulling on the reins: kisses, not bites; prefer long strokes to short ones; offer a slower decay without being slow, but perhaps for that very reason they deliver a more friendly or "musical" sound; they are not a layering monster, although, in this aspect, they sound better with the OOR than with the ACRO: no doubt, they ask for a bit of current to loosen up. VERY enjoyable.
The CHARYBDIS are cool—not ice-cold—water in the face. The CALDERA, a blanket on your lap in the evening. Pilsen vs "toast". Macallan vs Lagavulin. The CALDERA are a Mediterranean woman. The CHARYBDIS, on the other hand, a Slavic woman, not much given to caresses, but honest: she always comes from the face. I can understand that the CALDERA are more attractive. You could have them as the only headset —it plays a lot of sticks— and be happy. However...