You know my opinion on this matter, but just to be public about it: I would vote strongly for Git. Mercurial has its users, but in terms of community mindshare, there is no stopping Git at this point. It’s the system people are migrating to, the one it’s easier to get help with, the one more people are preferring. Of course those are all pragmatic reasons which do not address its technical merits, but it is either superior on its merits or close enough not to matter (depending on how persuasive any one person finds the technical arguments to be).
As for lack of Git knowledge being a barrier, I think the general trend is that the Git—and more specifically, the GitHub—model of social coding encourage contributions much more than SVN does. It doesn’t seem obvious why this would be the case, but it is a consistent message I am beginning hear from people who run open-source projects after having done the migration.
I would love for 2.1 to be hosted on GitHub, and I’ve love to help with the migration.