Github is better. It just is. You don't have to worry about backups, it has great tools built on top of the vcs to make working with it and project management easier. It makes it easier to manage the D part of DVCS, and it lets you easily put your tools into the community.
If you run an open-source project, the community is on Github and that's where they expect to file bugs. Most users/contributors already have their notifications tweaked the way that they like, understand the workflow and website, etc.
At this point, Github is in the same league as Wikipedia in terms of "a fantastic story of technology helping people to create ad-hoc, altruistic collaborations".
The question I'm asking is whether it's better enough to justify a vast investment. New businesses -- startups -- need to take actions to conserve their cash, and sometimes "good enough" is good enough.
It's especially important to get this right when one choice is an unprofitable unicorn-style company with vast cash outflow.
I suspect they see it as a charity case, if true.