Shawnlh, I haven't personally made the comparison, but I have an industry insider friend who rolls lots of top cartridges, and who positions the AT ART7 & ART9 above both the Kleos and the Delos. I have an ART7 and will probably try an ART9. Reportedly the ART9 has a fuller and more dynamic presentation than the ART7(and a more phono stage friendly .5mV output.) I do have both ART7 and DL-S1 and prefer the ART7.
Whatever the merits of the AT ARTs, there are doubtless audiophiles who won't try them due to confirmation bias favoring higher priced brands.