LXC will be faster than Docker
Docker will have performance overhead compared to normal LXC containers due to Docker's use of layers of read only filesystems. Using aufs or layers of filesystems via device mapper as Docker does will inevitably have a performance hit and increases complexity.
IBM should have tested normal LXC containers to get an accurate result of container vs VM performance.
There is a lot of confusion and misinformation in the media about LXC and Docker and a real danger of conflating Linux containers (LXC) to Docker, which is a single use case of containers to build stateless applications as services, which contrary to popular perception makes it more complex it use than LXC.
Docker containers can only run a single process or application. Docker containers unlike normal LXC containers have no init service to manage a normal modern multiprocess OS environment, so you have to run php, nginx and mysql for instance in 3 containers. You can't run things like SSH, cron or a management agent in Docker containers as that would be a second process.
While stateless containers is a legitimate use case, it's still a use case (and one perhaps more suited to PAAS type vendors pursuing statelessness than average users ) and the media and blogosphere do a great disservice to the LXC project on which Docker was/is based, to readers and informed discussion by not articulating these critical differences and simply pushing Docker as Linux containers.