I’d argue it’s mostly polarizing; proponents love it, while detractors hate it. A nuanced discussion is what we’re missing…

It looks like the best options for immutable have a learning curve or time commitment attached (e.g. NixOS). For a daily driver computer it might be worth the trouble to learn, but in this case I decided to just go with standard Fedora XFCE for now.

Fam, don’t sleep on Endless OS.

VanillaOS and OpenSUSE immutable ones use BTRFS snapshots dont they?

For openSUSE’s atomic offerings, you’re correct. Vanilla OS is a bit more nuanced, though. I don’t quite recall how they did it on their original images. But since Orchid, there is a reliance on OCI images for its updates. Note that bootc is also contingent upon OCI images, which is why I made the comparison earlier. They behave so similar to one another, that Vanilla OS’ Vib can be used (without too much trouble) to create Fedora Atomic images.

As for the usage of Btrfs snapshots on Vanilla OS, I think it doesn’t quite need it because it relies on lvm thin provisioning instead for its ABRoot. However, an attempt to verify this by installing it within a VM failed spectacularly and I don’t think the blame is on me 😅…

Sorry, perhaps I should have been more clear.

It was meant strictly in the sense of how much it burdens the system performance-wise. So, in other words, using nix is easier on your system’s resources than rpm-ostree (or bootc) is; at least, that has been my experience.

In regards to breaking, I’m not sure whether one outdoes the other. Though, I suppose that nix -by design- would inch this out. But this is basically an ‘internal dispute’ between the crème de la crème; as rpm-ostree/bootc basically outdoes any other distro package manager that’s not named nix or guix.

While I absolutely adore everything rpm-ostree/bootc, I do think operations involving it are relatively heavy; at least compared to what else is out there.

Depending on your (in)tolerance, you might therefore consider opting for something else, instead. Assuming that this list does a considerable job at presenting your options, I’ll try to provide input on some of the more mainstream ones:

• openSUSE’s offerings. AFAIK, it is lighter. Heck, I’d reckon you might not even be able to distinguish it from its traditional counterpart; Tumbleweed. However, its ecosystem is still very much in its infancy. Hence, I don’t recall any of their offerings that don’t rely on GNOME/KDE-Plasma. There used to be Project Greybeard, but it’s far from lively… As for Aeon (i.e. GNOME version) and Kalpa (i.e. KDE Plasma version), they haven’t had a general availability release yet.
• NixOS. I have heard good things regarding how well it does on low-end PCs. However, FWIW, my own testing portrays a different story: I once had an update that resulted in a lot of compilation and my machine was struggling quite a bit. The same machine that handles Fedora Atomic quite gracefully*. Perhaps that was a fluke, but I wanted to point it out. I’d argue nix does handle operations more gracefully than rpm-ostree/bootc on average, though.
• Guix System. Perhaps I’m wrong, but I wouldn’t be surprised if this outdoes NixOS in terms of how gracefully it operates on a low-end system. This is mostly on vibes, though.
• Endless OS. If you liked Bazzite, but want something lighter, then this might be just that. It relies on ostree only and thus doesn’t have the heavier operations from rpm-ostree/bootc. The goals of the foundation behind it align with enabling low-end hardware. This is reflected in their system reqs. Note that GNOME is still relatively heavy, but you should be served well even on just 4 GB of RAM.
• ChromeOS Flex. For completeness’ sake, if you’re otherwise okay with this, then I suppose it’s another option worth considering. FWIW, there’s also FydeOS (and perhaps others).
• VanillaOS. Does something similar to bootc ever since its Orchid release. So, it’s probably not that light. Furthermore, I got many questions regarding the health of its ecosystem. This used to be another serious contender, but I’m afraid it might have missed the boat…
• GNOME OS and KDE Linux. While not production-ready yet, these will definitely be interesting in the long run.
• aerynOS. Another project that’s not production-ready yet.
• Nitrux. Definitely one of the more interesting ones. It has been around for quite a while now, but I’ve yet to come across someone that dailies it.

Having said all of that, the gist is basically that atomic distros are still relatively new. As such, I can only recommend Endless OS, Guix System and NixOS. Note that the latter two are rabbit holes, though.

A couple of years ago, I used both of them briefly and GNOME simply provided the more polished experience back then.

In time, I came to dislike the look/design of KDE apps.

So when the time came I wanted to ditch GNOME because I was sick of its extensions ecosystem, I didn’t even consider KDE Plasma. Instead, I tried out Sway and eventually settled on COSMIC.