One of my more favorite reasons to use Django would be - http://www.django-rest-framework.org/ - whose discoverable API browser is awesome and saves so much time in building out a great REST API with pagination, related resources, and so many other things (plus you can post from the API browser). A bit less so the built-in admin features, which are also nice at times. Possibly also the migrations system. I don't use Django templates, but the rest of it are pretty much great.

I almost started a very major project with Flask, but am glad I did not for how much work DJRF and South had saved.