This wasn't supposed to be about Git vs Mercurial. I should have been more clear in my post!
The reason it would make things easier if we switched to using Git on Bitbucket is because it would make things more streamlined. I don't like how I need to use Mercurial when I want to work on GDC, then switch back to Git when working on DMD. It would even be better if both projects were using the same hosting site.