I find the way your phrase that question interesting. Git and Mercurial are nearly identical in terms of functionality, to the point that converting back and forth between them is pretty trivial. (Example: here's Git's repository in Mercurial https://mirrors.kilnhg.com/Repo/Mirrors/From-Git/Git)

The only real difference between the two are the ecosystems. Mercurial, being written is Python, is very portable and easily extensible. I feel like, because of that, the tools for Mercurial are better. Git has GitHub, and the incredible open source community they've developed there.

* Note, the rainbow road is due to one of the few differences between Git and Hg: Hg does not allow octopus merges, so the conversion turns them to a sequence of two at a time merges. Also, in the interest of full disclosure, I'm one of the devs on Kiln, so I'm certainly biased towards Hg.