Do not confuse their solution with app containers . VZ is a system container solution which is a wast different beast than application containers like Docker and Rkt. VZ, LXC and LXD is system container software that run a full OS in container fashion. App containers are for running one or a few single application only.
VZ is a mature and good product. The drawback is that is requires a custom kernel, so one can not install and use vanilla RHEL/CentOS. I would pick LXC/LXD due to this big issue.