Docker and z/VM or KVM?

At LinuxCon, KVM for z has been announced. From a Docker perspective, what does KVM change over a z/VM environment? There's a pretty short answer: nothing. KVM is cool for a number of things, z/VM is still king of the road, PR/SM still has got some bragging rights, and Docker doesn't care, as long as a Linux runs in it. Docker under both z/VM and KVM benefits from complementing technologies.