Things have changed some since these answers were posted, but answers 2 and 3 here are written by the authors of vagrant and docker, respectively.

http://stackoverflow.com/questions/16647069/should-i-use-vag...

And the bonus of using Docker is you can use the same image you develop on to test with, and the same image you test with in production.

This not only avoids the "Dunno, works on my system" but also the "Dunno, works in dev/test"

A Vagrant VM is a full fledged environment, useful for thick stack setups such as LAMP or LAMR or MEAN. While you can somewhat abuse Docker to fit this role by using supervisord or somesuch, it is much more suited to having exactly one process per container.

You could potentially even combine the two approaches and have a Vagrant VM with a small Ubuntu stack that has docker installed and then have a set of docker containers, one per component or service.

That said, the Docker abuse setup is fairly common. I'm in the process of doing one myself right now. :)