I have build sites and services in both of them. I am definitely more familiar with Django. But using flask-batteries is just more work / LoC to use them. Building a feature without batteries is IMO nearly the same in time and LoC.

Of course you are more flexible and have a smaller default installation, which are great things, but most of the time Djangos batteries "just work" and every hour I can safe working on a project and still delivering the expected results is great for me and my clients.