I never understood the appeal of BSD jails over Solaris zones which seem to be more hardened and seem to vitualize more of the OS.
FreeBSD is the appeal.
Back in the earlier days of containerisation Linux had no options (Linux was pretty late to that particular game) and Solaris wasn’t free. So FreeBSD made a lot of sense.
These days the tooling around Linux is better and there are open source forks of Solaris so FreeBSD might seem like an odd choice for some. However I still think FreeBSD is a rock solid operating system and one that doesn’t get taken as seriously these days as it should do.
FreeBSD's appeal for me is the easy maintenance. Everything related to config is in /etc/rc.conf; tunables in /boot/loader.conf. The ZFS implementation is rock-solid. I therefore only have to fiddle with my FreeBSD server, running 80TB ZFS storage pool, once a year or so.
No other OS gives me this kind of comfort and stability.
I wonder if Solaris has bigger userbase it would also appeal to you.