On first look, both approaches look very similar.
No matter the fancy name used here, both are solutions to a specific problem: A better segregation solution than classic Unix chroot. Operating system-level virtualization, containers, zones, or even "chroot with steriods" are names or commercial titles that defines the same concept of userspace separation, but with different features.
Chroot was introduced on 18 March 1982, months before the release of 4.2BSD as a tool to test installation and build system, but for today it still have its flaws. Since the first objective of chroot was only to provide a newroot path, other aspects of system that needed to be isolated or controled got uncovered(network, process view, I/O throughput). This is where the first containers(User-level virtualization) appeared.
Both technologies(FreeBSD Jails and LXC) makes use of userspace isolation to provide another layer of security. This compartmentalisation will ensure that a determined process will communicate only with other processes on the same container at the same host, and if using any network resource to achieve "outside world" communication, all will be forwarded to the assigned interface/channel that this container have.
Both technologies are not security panaceas, but are pretty good ways to isolate an environment that dont require Full Virtualization due to mixed operating systems infrastructure. Security will come after a lot of documentation reading and implementation of kernel tunnables, MAC and isolations that those OS-Level virt offer to you.