Why LXD instead of Docker?
A quickly looked up answer to "Why use LXD instead of Docker?"
Multiple processes can run inside the same container. It can run a single process per container which means that if one wants to run a z number of processes, one needs a z number of containers to run that process. LXD is faster than Docker for executing applications while using multiple processors.
However, I don't believe that is true - any number of processes can run in a single container. However, it's typically cleaner to separate out.
Maybe somebody can explain why they use it?