Personally all my own projects are on bitbucket. They were the first to provide free unlimited private repos and just has a great set of tools. So my personal preference is bitbucket over github.
Not trying to start the classic hg vs git debate, just saying that it's great to have the option.
(hate it when companies do this)
Bitbucket Server is written in Java and bitbucket.org is written in Python.
I was dumbfounded when I found out they were two separate codebases.
https://www.mercurial-scm.org/repo/hg/
Mercurial is very important for Facebook, Mozilla, Google, and others. The disparaging "legacy" monicker might be a good way to feel justified to not have to learn about it, but it's not dying software that is no longer getting updates.
Check our RhodeCode for Enterprise SCM tool that supports Mercurial too.