SwampDragon is a more comprehensive solution. It comes with a JS client and lets you define data models. Pushpin is lower level. It has no client protocol nor client library and handles various push primitives on behalf of the backend.
If you want to add realtime endpoints to an existing Django project, or if you want to build an API, then Pushpin may be preferable. SwampDragan may be preferable for new, non-API projects.
It might be cool to see the two projects integrate somehow, since they actually sit at different levels in the stack. There could be value in SwampDragon being able to delegate push responsibility to Pushpin.
If you want to add realtime endpoints to an existing Django project, or if you want to build an API, then Pushpin may be preferable. SwampDragan may be preferable for new, non-API projects.
It might be cool to see the two projects integrate somehow, since they actually sit at different levels in the stack. There could be value in SwampDragon being able to delegate push responsibility to Pushpin.