Could you outline what it is that you think makes Git better?

From my daily experience with both Mercurial and Git, i would say the exact opposite. I can't think of anything that Git does better than Mercurial. I can certainly think of things it does in a needlessly more complicated way - the handling of remote tracking branches and the use of the index are obvious ones. Git's fixation on branches over commits is a persistent deep source of pain for users around me. And you can pry revsets from my cold, dead hands.

Now, there was a time when Mercurial didn't have bookmarks. During that time, if you wanted a good lightweight branching model, Git was your only option (er, well maybe bzr or Darcs were, who knows). I was never that excited about lightweight branching; the weight of heavyweight branches does not seem substantial. Today, Mercurial has bookmarks that work pretty much like Git branches, so this advantage has evaporated.