Mobile App. Start with Service Workers and PWA and decide then if you need an app.
Whereas with Rails your stack traces are much longer and there's a lot more machinery each request has to go through. Rails has a lot more abstraction in general (you can blame Ruby's powerful reflection capabilities on that), but I found that I have to go delving into Rails' internals very little.
What you get with Django but not with Rails:
- An admin panel out of the box
- Python (which is a big win for me personally)
- Authentication out of the box, but still fairly basic
- A robust library of third party packages that benefits from python being used much broader than the web space.
- Class based views (this is the biggest thing I miss, by _far_)
- Better LSP support
- Django REST framework (rails isn't _quite_ as good but you can get kinda close by leveraging resourceful routing and the serializers that ship with rails)
What you get with Rails but not with Django:
- Websocket support out of the box (but not the greatest performance. A third party drop in replacement [Anycable] makes it much better)
- First party API for background jobs (but it requires a third party background job system to wrap, like sidekiq)
- First party integration of a JS solution (import maps)
- Second party integration of a JS bundler (js-bundling, written by rails authors but not included by default)
- Hotwire (although Django trivially integrates w/ a comparable technology, htmx, Hotwire is still pretty dope)
- Rspec and the rest of the Rails testing ecosystem (guard, VCR, factory_bot, capybara). Python has ports of some but not all.
In my mind, Django adopted just two things, I'd be very happy. I'd love to see a better async story in Django that would enable web sockets and stuff. And the second thing I'd love to see is a better story out of the box for playing nice with frontend build chains. And, as a distant third, I'd like to see an html-over-the-wire technology like HTMX favored and some light integration in Django to recognize some headers so it can switch between sending just template segments or if it should send one w/ the layout included. The testing ecosystem I don't think is possible for Django to lift on it's own and I'm prepared to miss it while I'm away. That other stuff, though, is unfairly aging Django imo.