1. Built using DevOps tools widely in use (i.e. Chef) so it integrates easily into most environments and is an easier sell to conservative Ops teams
2. Implemented with Django, Celery and other components that may not be as sexy as writing from scratch in Go, but are battle tested -- which is a big plus for application platforms.
In my opinion, there's room for both approaches in the Docker PaaS world.
1. implemented in Go vs. Python+Ruby which means no dependencies, easier install, etc.
2. Modular architecture: in addition to Docker will also use CoreOS and etcd.