A little bit of background: I learned Django first. Then I learned Rails via Code School, and flirted with building my app with Rails instead of Django. I saw the asset pipeline specifically as a Rails advantage over Django (I write Emblem, indented Sass, and CoffeeScript whenever I can avoid HTML/Handlebars, CSS, and JS). Also, building JSON APIs with Rails has better out-of-the-box support than it does in Django.

I always felt Rails' model layer is clunky compared to Django's. What is the definitive representation of my model? The validations in SomeModel < ActiveRecord::Base or what's automatically generated in schema.rb when I run migrations via Rake? In Django everything, including migrations (in simple cases), is derived from the classes in models.py. But I thought it would be worth it to persevere, due to the above-mentioned advantages.

Then I realized I could (and should) compile assets via Ember-CLI, and Django Rest Framework is just a pip install away. So the two main advantages of Rails disappeared, and switching back to Django became, for me, a no-brainer.

Edit: I also prefer Django's less magical approach. This may seem ironic given my love of Ember, but Ember's magic is easier for me to understand than that of Rails.

Personal opinion, obviously, but I also find Rails to be way too magical sometimes.

I am also a Rails dev, but one feature I think Django really got right that is head and shoulders above Rails are Form Objects (https://docs.djangoproject.com/en/1.9/topics/forms/). Rails' attr_accessible stuff and even strong_parameters really pales in comparison.

I do rendering on the client-side, so do not use Django's Forms. But there are ModelForms which integrate seamlessly with your model because it is the definitive representation of a real-world object.

Similarly, Django Rest Framework has ModelSerializers and ModelViewSets which give you a lot of free functionality out-of-the-box precisely because Django's Model layer was designed with DRY in mind.