There isn't much of a difference. The underlying principles of how they work are essentially the same. However hg has IMHO a more pleasant UI, and it's easier to customise. I believe Facebook chose hg for the latter reason: https://code.facebook.com/posts/218678814984400/scaling-merc...

I like the simplicity and the better Windows support. Many things in git rely on you having a powerful shell, which is not the case on Windows (who wants to use cygwin all the time?).

In Mercurial I never lost a commit, even as a beginner. In git I managed to accidentally make commits unreachable (yes, I know how to recover, but still, it tooks a bit of googling and trying).

I very rarely need git's "remotes" feature. There's rarely a need for me to know where someone else's master is at the moment. I understand why git is doing this and I get that it's pretty flexible, but most of the time Mercurial's simple branching model is enough for me (I don't like bookmarks, they confuse the hell out of me).

Also, my repositories are usually small enough that I don't notice the Python overhead compared to Git. My ultra slow old disk is more of a problem in that case.

Mercurial's help is MUCH better than git's. Git's manpages are so famous for being mostly useless that people even write joke tools that generate gibberish manpages. Mercurial has a very clean documentation, with `hg help ...` just showing you what you need to know instead of (on Windows) using your browser to render an HTML manpage.

And lastly: Will git 2.0 ever come out for Windows? Seems like nobody is working on that, so we Windows users still get some preview version 1.9.4 at the moment. That doesn't look to me as if Windows was a first-class citizen in git.

Fun fact: Converting from git to mercurial is the easiest thing in the world (`hg convert my-git-repo new-hg-repo`), but the other way around is weird and complicated to setup (talking about hg-git).