Having heard both of these cartridges and now owning a Kleos, one thing is certain, that is both require a very very precise set-up. Even the slightest error and you simply won't hear what these cartridges are capable of. IME, the Kleos is a lot more accurate sounding and more resolved at both ends of the spectrum to the Delos. The Delos may work in more set ups, as i suspect it is a tad more forgiving, and it seems to work with a wider range of loading. Nonetheless, the Kleos reminds me a lot more of the top of the line Atlas, as it probably should as the design shares a number of similarities.