See how the leading CoreOS Container Linux alternatives stack up against each other, or scroll down to the conclusion if you just want to get to the bottom line.
Flatcar Container Linux
And the winner is…
All of them!
There is no single "bottom line" because the path you choose depends on your needs and use case.
Instead, here are some recommendations based on some common scenarios.
If you are using Red Hat OpenShift
…then you should use RHEL CoreOS: it is bundled with your existing subscription, and fully integrated and supported.
If you want a seamless in-place upgrade for an existing CoreOS Container Linux deployment
…then Flatcar Container Linux is the only solution meeting your needs today.
If you want to try a cutting-edge operating system with the latest features, and are willing to live with occasional regressions or breaking changes and best-efforts community support (rather than a commercial support contract)
…then consider either Fedora CoreOS or the Flatcar Edge channel. Both are good solutions.
If you want a container-optimized operating system with enterprise support AND you’re not using Red Hat OpenShift
…then you should use Flatcar Container Linux with a support subscription from Kinvolk. It is the only solution offering that capability today.
If you will only deploy on AWS, want an OS that is backed up by Amazon, and are willing to try something that’s not yet a stable, generally available release
… then Bottlerocket may be worth a look for you. However, Fedora CoreOS or Flatcar Container Linux will both give you essentially the same functionality, but with a more mature project and from platform-neutral project teams.