Beyerdynamic - DT 1990 Pro MK II vs Sennheiser - HD 660S2

The DT 1990 Pro MK II edges ahead on the Mars Score (66.2 vs 61.4), but the 4.8-point gap is small enough that the right pick comes down to which spec advantages matter to you.

Pick the DT 1990 Pro MK II if you care most about driver size. The biggest gaps in its favor are driver size.

Pick the HD 660S2 if you carry the device everywhere and weight or thickness has been the deciding factor before. Its strongest claims are weight.

Both ship with comparable battery life, active noise cancellation, spatial audio, 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.