NightOwl is smoother and deeper, richer and lusher. And yes, it is capable is rendering those finer details, but due to its tuning (warmer), details are not what will shoot out at you when compairing to the 99 Classics. The 99c has more treble energy and is brighter up top, which is traditionally better for detail retrieval. NO is a superior headphone and can get there without that tuning, though it won't be as apparent.
Just be careful that warmer and richer is what you want.
Also, NightOwl is WAY more comfortable that Meze. I find Meze acceptably comfortable, but NO takes it to a whole new level.