The two came out at roughly the same time and for the first few years it wasn't really obvious which was better.
Personally, I chose Mercurial to start with, because I liked the Windows tooling available and it felt a lot more like Subversion, which is what I used previously.
However, Git won the mindshare war in the end, so I moved over to that.
Happened the SAME thing to me. Mercurial felt more natural than git. Back then, Github allowed you to choose the VC and Mercurial and Git were available, I'd always choose Mercurial. I was also using Google Code that allowed for mercurial as well.
Oh that's right - I'd forgotten about that april fools joke that wasn't. It was just client compatibility right - the backend was still git from memory?
What I mean was that it wasn't like Bitbucket where you chose whether you wanted git or hg for starting your project.
The Xen Project chose Mercurial to replace Bitkeeper (the proprietary but free-as-in-beer-to-open-source-projects-for-a-while VCS that Linux used before it became no-longer-free-as-in-beer) as well. There were things that were nicer about it; but in the end it just made more sense to move over to git.
That was over a decade ago, however; I'm actually pretty surprised it took Mozilla so long to switch.
12 years ago I decided to try using Mercurial for tracking history of my plain text notes. I chose Mercurial for it's supposed better Windows support. Turned out that it couldn't work with unicode filenames. While git could.
After all the years, do you think mercurial still offers tangible benefits in terms of versionning workflow ? faster operations, more extensibility, things that are somehow only possible in hg and not git (or way too hard in git)
I'm a happy git user but I'm really curious about losing good ideas from other tools due to mindshare.
I now haven't used Mercurial in about 8-10 years or so. However, I recall enjoying the workflow a bit more, and I did like how commits were explicitly linked to branches as opposed to branches being effectively pointers to commits - it was nice to find out the original branch of any given commit.
However the killer feature of Git is the ecosystem. I was always having to do lots of custom work to get Mercurial to work with CI providers, whereas Git just worked and had first class support. It was clear after a while that our team would always be outsiders if we continued down that path, and there wasn't enough of a compelling reason to stay with Mercurial.
Personally, I chose Mercurial to start with, because I liked the Windows tooling available and it felt a lot more like Subversion, which is what I used previously.
However, Git won the mindshare war in the end, so I moved over to that.