If only one of the BSDs had a container runtime, it's the only real showstopper for me
jails were/are common in the webhosting and gaming industries, and nowdays they can be managed with infrastructure-as-code tools like ansible or puppet. when backed by zfs, they can be made to behave very similarly to docker containers.
with the demise of docker the company and the fractured ecosystem of competing container runtimes, specifications, kernel compatibility issues, and management tools, jails are worth testing out. iocage is one way to start managing them.
Most of the container use-cases that aren’t layers work fine under jails. But it’s a more primitive tool, definitely not as user friendly.
I'm pretty sure that with unionfs you could get layer-ish equivalent for most use cases. Not going to question that it wouldn't be user friendly though
Neither one of them was delivering usable experience.
UnionFS is broken and not recommended to use. ZFS snapshots aren't layers. FreeBSD has loosely coupled tools to make something like docker, but nothing remotely close to full docker is available atm.