Well, the difference is the entire ecosystem of nodejs is built around async. Fitting it into python is very hard, and you better have a really good reason for trying it. It just doesn't interact favorably with a lot of common python tools (Sqlalchemy being one example)
This. Flask can technically run in an async event loop (see:
http://docs.gunicorn.org/en/stable/settings.html). But gevent is a massive monkey-patch on top of Python standard libs to make them async friendly.
If you're hitting enough load where async really matters, just skip Python altogether. And please, please, don't use Node. Just use Golang or Scala for true multithreading, and you'll save yourself the headaches Javascript will bring for something that's not truly parallelized.
