I've never hidden my admiration for #illumos-based systems. I have a few setups based on #OmniOS and #SmartOS, and they're solid as a rock. I like them both: OmniOS is more "malleable", while SmartOS is more of a hypervisor like #xcp-ng or #xen - meaning you install it on the host and delegate everything else to the zones.
I also love #FreeBSD jails, but zones sometimes cover use cases that jails can't (and vice versa). For example, imposing RAM limits in jails works, but it effectively "denies more ram" to a process when it requests more memory. The end user doesn't see this directly. On illumos, the user sees everything. I have some `lx` zones with Debian and Virtualmin, and users have never noticed that they aren't really on #Linux. A free or top will show only the assigned RAM.
And that's one of the biggest problems with open-source operating systems: they all have something good, and I always feel the urge to use them all! 