There is a noticeable difference in weight (NA vs 131 g), which may affect comfort during extended use. Koss QZ99 and Beyerdynamic DTX 350M are well-known options in the wireless headphone segment, offering a balance of audio quality, battery performance, and smart features. The frequency response differs (40 Hz - 20000 Hz vs 22 - 18,000 Hz), which can influence how well the headphones reproduce lows, mids, and highs. Both headphones are equipped with capable drivers that deliver balanced sound output suitable for music, calls, and entertainment. Both models support modern Bluetooth connectivity, ensuring stable wireless performance with compatible devices. Both headphones offer solid battery performance, making them suitable for long listening sessions and travel. Impedance levels vary (60 Ohms vs 32 ohm), which can affect compatibility and audio output when used with different devices. Koss QZ99 and Beyerdynamic DTX 350M offer different noise cancellation capabilities (Yes vs NA), which can impact how effectively they block external noise. From a usability standpoint, both models provide a reliable and premium headphone experience.

Verdict: Both headphones offer strong performance, and the right choice depends on your priorities such as battery life, comfort, and noise cancellation.