Modern tango versus traditional tango

I've only learned tango from a few teachers, all from the same school and they all teach the same "style", but the other night, at a milonga, someone made the comment that a surprising number of dancers danced very "modern tango", but most of "us" danced "traditional" tango.

I could see the difference, I think, but couldn't really put it into words.

What are the "technical" differences between old and new tango and which one do you dance?

C'mon peoples. Work with me.