As I said in my title, I ask which (or maybe the both) of data-vocabulary or Schema.org we should use ?
I know that Schema.org is the one recommanded by google, but i can see data-vocabulary on many website. And I even see the both on a single page !
Both are fine. I wouldn’t mix and match!
I will say however that (personally, anecdotally) I have seen better search results from well implemented schema’d sites than other microformats.