The cloud part makes much more sense when combining it with the user land. I think that's also where OpenBSD (or *BSD in general) really shines, everything is very coherent. Regarding Linux, I'd probably see CentOS/RHEL as "modern hardened cloud OS" with all it's measures in place. But even as a complete BSD beginner, I find OpenBSD or FreeBSD easier to configure than CentOS, which IIRC requires a lot of manual whitelisting of capabilities for server daemons.