Serious question... are you using HG because of history, or do people actively choose HG over Git for new projects still?
Have used both, they are so close, seems "odd" to go for the way less popular one, barring you have a really old HG repo and haven't bothered to switch.
I prefer mercurial over git and will choose it every time for new projects unless there's some other concern preventing that.
Mercurial has a number of features that git never implemented - in particular revsets. I also prefer the hg CLI over the git CLI. Mercurial has sane, concise online help, and a lot of work went into the design of the command-line to be consistent, composable, and made of pieces that do one thing and do it well.
Seconding this sentiment. Far, far, prefer hg to git. TortoiseHg blows away the Git UI's as well, IMO. I always feel like i'm poking around in the dark on SourceTree.