git is 10 years old [1]. mercurial is 9 years old [2]. git won.

Way back when I was looking at both (7 years ago maybe?), it seemed that mercurial's main selling point was functional equivalence to git with a "better" architecture and source language. This is the ultimate case study in the fact that neither of those things matter to users (even deeply technical users) unless they impact user experience (stability, performance, UI, etc).

[1]: http://en.wikipedia.org/wiki/Git_(software) [2]: http://en.wikipedia.org/wiki/Mercurial