Personally, I'd go for the 2012 certificates.

They are a bit harder to get than the 2008 exams (you now have to do three exams), but you get to know the latest features.

If you can pass the 2012 exams, you should be able to pass the 2008 exams, in theory.

Do the 2012 certifications have a bigger significance in the market place?

Hard to say. You can question yourself if they have any significance at all, because they are so easy to cheat.