In real world listening, the noise performance is the most important thing. If anything is audible, other than frequency response, it will be noise. I found that high frequency noise even it's not that audible by itself, alters your perception of sound when you play music. And you can really hear the noise in late night with a quiet environment. Reducing the noise drastically can slightly make the sound more rounded, deeper, less "exciting"/irritating. It's very important for low impedance headphone/earphones.