Both models support modern Bluetooth connectivity, ensuring stable wireless performance with compatible devices. The driver size differs between the two (38 mm vs 70 mm), which can influence sound depth, bass response, and overall audio clarity. If you're comparing Sennheiser HD 660S2 and Sony MDR-Z7M2, both models offer a strong combination of sound performance, comfort, and modern wireless features. There is a noticeable difference in weight (260 Gm vs 340 Gm), which may affect comfort during extended use. Impedance levels vary (300 ohm vs 56 ohm), which can affect compatibility and audio output when used with different devices. The frequency response differs (8 Hz -41500 Hz vs 4 Hz - 100000 Hz), which can influence how well the headphones reproduce lows, mids, and highs. In general, both options are suitable for everyday use including music, calls, travel, and work-from-home scenarios. Both headphones offer solid battery performance, making them suitable for long listening sessions and travel. Sennheiser HD 660S2 and Sony MDR-Z7M2 offer different noise cancellation capabilities (AMBIENT vs NA), which can impact how effectively they block external noise.

Verdict: Both models are competitive, and your decision should be based on your usage needs and preferred features.