+1  A: 

Best is a subjective term. I suggest you try both Git and Mercurial, since those two seem to be the most popular; both have several free hosting sites (Mercurial is directly supported by Google Code, although you can use git-svn with Google Code, while Git has Gitorious and GitHub) and are well-liked.

Michael Aaron Safyan
A: 

There's no reason not to just try the big contenders out, get a feel for what's available, costs you nothing but a small amount of time, and could save you a change of your first choice later.

  • Pick an open source repo on bitbucket & github.
  • Check out and try making commits against the bitbucket one via mercurial.
  • Do the same with git.

  • If you're really interested in development on bazaar, do the same with bazaar. Do them in that order of importance, since your a heavy windows user.

Tchalvak