Pretty good post from Martin Fowloer on Version Control Tools.
What he says on git :
Git certainly seems to be liked for its power. Folks go ga-ga over it’s near-magical ability to do textual merges automatically and correctly, even in the face of file renames. I haven’t seen any objective tests comparing merge capabilities, but the subjective opinion favors git.
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For many git’s biggest downside was its oft-cryptic commands and mental model. Ben Butler-Cole phrased it beautifully: “there is this amazingly powerful thing writhing around in there that will basically do everything I could possibly ask of it if only I knew how.” To its detractors, git lacks discoverability – the ability to gradual infer what it does from it’s apparent design. Git’s advocates say that much of this is because it uses a different mental model to other VCSs, so you have to do more unlearn your knowledge of VCS to appreciate git. Whatever the reason git seems to be attractive more to those who enjoy learning the internals while mercurial seems to appeal more to those who just want to do version control.
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People generally find that git handles branching better than Mercurial, particular for short-lived branches for experimentation and check-pointing. Mercurial encourages other mechanisms, such as fast cloning of separate repository directories and queue patching, but git’s branching is a simpler and better model.