And yes, this is the company I work for and this will be the DVCS I will have to use. ;-)
git is fine I suppose - but we needed to support Windows and I'd rather know that Windows is supported properly (mercurial), rather than kinda hoping it works (git). Things might have changed since the last time I looked.
In either case, be careful with case-sensitive/non-sensitive file systems.
Also, consider the learning curve difference as you will suddenly become the go-to guy for issues.
In the end, I'm really a Bond fan: http://importantshock.wordpress.com/2008/08/07/git-vs-mercur...
Personally, I feel that git is technically superior, but throwing Windows into the mix changes things up a bit. You can use git confidently in Windows - I do at home, using Cygwin - but in terms of graphical support, it's still reasonably dodgy. You could definitely look into TortoiseGit, and then configure it using mSysGit and putty (I've tried this in the past and it works well) - but if anyone then wants to use Cygwin, things get very complex.
GitX is good for Mac users though!
might be worth a look
If you still need more information to be sure, I think I trust these two, esp recommend the google code link.
http://code.google.com/p/support/wiki/DVCSAnalysis
http://rg03.wordpress.com/2009/04/07/mercurial-vs-git/ This one is a little balanced. more like a good info on internals of both. A little too long, and I didn't like the fact that the guy says both are great, in summary. I knew that already...pick a side if u write a VS article...or else what's the point.....
I take my words back (if that's ever possible :) ).
I assumed the purpose of writing that article as saying I pick this, if pushed to the corner (as is the case in our startups).
I will have to say it's a fairly good introduction. I like the amount of details provided.
As far as I know, git is a bit more flexible than mercurial, in the sense that each user can use it the way they like to (with things like quilt --- and here I'm sure someone's going to yell "but mercurial has patch queues by default!!1"), without screwing up or imposing on everyone else's workflow. I'm not sure if mercurial does this, but I can't imagine anything doing it better than git.
That said, they aren't that different I don't think, so I'm sure you'll be happy either way, and each one will have its own wonkiness that you'll come to hate eventually.
May I add that Mercurial has Python dependencies, while git are written in C.
If I were to bet who outlasts who, I would put my money on GIT. Also, considering GIT is so simple by design, I foresee it will be used in many other cases than source code management. As it is just a matter of creating new high level porcelain, like say, revision control. ;) How about that Linus?
What makes a size 16 spanner better than a size 15 spanner?
Mercurial is used and backed by large projects like Mozilla, Google Code, OpenOffice, Solaris, and Python. (In my own opinion, git and mercurial are both best-of-breed, and I'm a happy user of both tools.)