Sennheiser - HD 660S2 vs Sony - WH-CH720N

These two are evenly matched on the broad strokes, with the decision sitting on which individual spec advantages weigh more for your use.

Pick the HD 660S2 if you care most about driver size. The biggest gaps in its favor are driver size.

Pick the WH-CH720N if you carry the device everywhere and weight or thickness has been the deciding factor before. Its strongest claims are weight, active noise cancellation, multipoint, among others.

Both ship with comparable spatial audio, ldac, water resistance, so those specs don't separate the two — focus on the differences below.

Bottom line: there is no wrong answer here — match the spec advantages to how you actually use the product. The Mars Score parity tells you both are well-rounded; the differences are about trade-offs, not quality.