Well, AFAIR (as far as i read), LXC are C and python and Docker is go-friendly, so recently they included libcontainer and slowly will remove the piggybacking on LXCs, i feel so, its optional with new release.
http://blog.docker.com/2014/03/docker-0-9-introducing-execut...
So in that case, they will bring along more features too,that will surpass LXCs.Also its the matter of statefulness and statelessness. LXCs are stateful and dockers are stateless so this is a big win here for dockers. Libcontainer brings more dimensions to dockers. So if state is not a concern for you, LXCs are any day great ones to go for.