Updated SteamOS partner guidelines seem to point to an imminent full-scale launch of SteamOS on other gaming handhelds out of the box, nevermind simply as an ISO for gamers to install on their own machines. Previous work suggests the Asus ROG Ally may be among the first to receive "Powered by SteamOS" certification.
The main advantages of Bazzite versus SteamOS is receiving system packages in updates at a much faster rate, choice of an alternative desktop environment, Waydroid support, layering system-level packages at your own risk without messing with the filesystem, and printing support.
From their FAQ page https://docs.bazzite.gg/General/FAQ/
Pretty much all linux distros have printing support
Except SteamOS, as I discovered when I needed it badly.
Still, I’m sticking to SteamOS on the deck and Bazzite for the desktop.