I have used both Ruby on Rails and Django in large production web applications over 2+ years. Speaking strictly about the web framework, RoR is the slightly better framework IMHO. This includes but is not limited to:

- cleaner internal APIs, models, methods

- a lot more stuff that "just works" out of the box where you would need a third-party package in Django (e.g. RoR gives you different settings for development/staging/production out of the box)

- better static file handling

- third-party packages tend to be a bit more mature and stable in the RoR world

However, using Django gives you easy access to the rest of the Python ecosystem, including all the data science and ML tooling. And that trade is worth it. So if you are starting from scratch today, i'd go with Django.