Git made it easier to fix problems when I screwed up my repo. Mercurial was great when everything was working correctly, but for a long time it lacked the tools (or required third party tools) to fix problems I ran into.

Mercurial did have one killer feature, and that was hginit.com. Git's documentation was terrible for a long time. I would send programmers used to old fashion version control to hginit all the time, even when I was teaching Git.