This is what made me choose Mercurial in my recent search. http://www.python.org/dev/peps/pep-0374/
There is a tremendous amount of detail there. In summary, hg and git are both very good, and essentially equal in features. The only salient difference is that hg is implemented in python, so they went with that. I did the same, and I'm quite happy. It's basically svn with the shiny new distributed features added. -- http://mail.python.org/mailman/listinfo/python-list
