Steam OS is a rolling release (Arch based) with constant small updates. My Steamdeck has had updates several times this year.

It's snapshotted from Arch, once a year they bump the kernel and include "updated Arch Linux base" as a release note.

SteamOS 3.7 is still on Kernel 6.11 and KDE Plasma 6.2, for example. Bazzite is 6.17 and Plasma 6.5.

This matters if you're using more recent hardware or want the latest driver optimizations. My 9070 XT is supported by Bazzite, SteamOS won't even boot.

I think that's changed recently. Recent release notes state it's added support for RDNA4

VKD3D-Proton gained FSR4 support and will ship in a future release of Proton, but RDNA4 requires a newer kernel.

SteamOS release notes are public at https://www.steamdeck.com/en/news, it still uses a 6.11 kernel from September 2024.

This youtuber has the 9070XT working on the latest steamos https://www.youtube.com/watch?v=_U6-R6XtCUQ&pp=ygUXZXRhIHBya....

SteamOS main is on Kernel 6.16.12 and KDE Plasma 6.4.3

My point exactly, main is SteamOS's alpha state before its frozen into 3.8 beta, and its still months behind Bazzite.

Especially on the Beta branch, I'm getting several system updates per week. I check for one every time I wake it up, along with checking for any available game update downloads. Originally moved to the Beta branch to get the new 8BitDo controller features (Mid-July maybe), but it's worked well enough I've never gone back to Stable.