Source is this video:
Windows Was The Problem All Along - Dave2D
We could obviously compare performance between windows and steamOS before on the steam deck, or between windows and Bazzite on other handhelds. But this is the first time we have had official windows and SteamOS builds for the same hardware.
Back in ~2010, my first dual boot was an Ubuntu. It was fairly easy to run WoW from Linux and it gave me a solid >15fps while Windows ran at less than 10fps.
I was very young at the time but still aware that this was super impressive with extra compatibility layers. That definitely took part in selling Linux to me.