This review brings up an interesting point, where they measured that at same-dB the fan sounds better because it has greatly reduced high-frequency noise (the second half of the review focuses a lot on this). I’d be interested in a [quantitative] comparison using something like sone.

Edit: NON-normalized spectrum analysis in Audacity (non-linear) and Spek (linear) using the +20dB audio clips: https://files.catbox.moe/h0hlvk.webp

Same thing but RMS normalized to -20dB: https://files.catbox.moe/38ugao.webp

These (particularly the normalized one) make it seem like the difference isn’t high frequency response (if anything the Metal has more lol), but instead reduced tonality.