Django+MongoDB vs Node.js+MongoDB
If you're looking for performance, Node.js should have a better performance against Django. But Node.js runs async, you should prepare the code for that, if you need everything sync and up, maybe Django is the best choice, because you already have it running.
But if you choose Node.js, make something that make the fact of beeing async is no problem for you and your data consistency, like message queues.
Check this out, it has the pros and cons of each one