Strictly speaking in terms of audio, many DAW benchmarks between Win 7 and Win 8 on the same hardware have shown little to no performance improvement in Windows 8… sometimes it’s even slightly worse. We’re talking 0-2% difference, in either direction.
I did some benchmarking for a review I wrote on the Intel NUC last year, and here were my scores between Win 7 and Win 8.1 for Cubase 7.5 DAWBench, Passmark Performance Test, and Windows Experience Index:
(Scores highlighted in green are better.)
Windows 8 boots faster and launches programs faster, but that’s it.
I’m waiting until Steinberg (and Roland) give Windows 10 the green light, and then I will do some benchmarking of my own on Win 10, but Windows 8 was an easy pass.