Like stormbrew said, it's all in what you are used to. We currently have both a mercurial and a number of git repos for various projects, and we are seriously considering spending the time to migrate the mercurial repo to git. The context switching from one to the other is really hard, commands don't work the way you expect and things just feel wrong.

Personally, I much prefer git, and I researched both before I used either. But I wouldn't fault someone for preferring mercurial, particularly if part of the reason was that they were very comfortable using it.