Honestly I think it's mainly due to the fact that git and github have a greater mindshare than hg and bitbucket. That said I think either choice is great, they

Honestly I think it's mainly due to the fact that git and github have a greater mindshare than hg and bitbucket. That said I think either choice is great, they are solid and mature implementations of the DVCS paradigm and are miles ahead of older systems like SVN. I use a mix of both personally, hg at work and git/github for personal projects.