(noticed your reply to my other comment too, please consider this a reply to both)
I wasn't aware of HP-UX Virtual Vaults, thanks. However, I'd say FreeBSD Jails still had an advantage, due to being free and running on various hardware platforms, and more importantly on commodity hardware.
Eventually they were replaced by HP-UX Containers (SRP) a couple of years later.
Unfortunately it is hard to still find documentation, given the troubles HP-UX has gone through at HP (which kind of plays into your remark regarding FreeBSD).
