If all the OS does is provide a minimal surface for running containers, I'd focus on whatever gives me the best security, manageability and updates.

The Container Optimised OS is what GKE uses on Google Cloud Platform https://cloud.google.com/container-optimized-os/docs/

It's conceptually very similar to CoreOS' Container Linux, so I might try that if I were looking at Kubernetes elsewhere and wanted a container-only OS.

If I am running an environment with multiple purposes - some container hosts, some regular machines - I'd err on the side of "who is my current vendor/what does my ops team support and know best".