Just an addendum to the Github numbers, I hadn't realized Adrian Holovaty had renamed the previous Github repository to django-old, replacing it with the brand new repository (with the SVN history, etc).

So if you look at django-old's numbers: https://github.com/django/django-old

Watchers: 4,030

Forks: 753

compared to Bitbucket's:

Followers: 266

Forks: 39

So the raw numbers are dramatically in Github's favour.