Probably the biggest difference (and most critical) is that they believe in a hereditary system of leaders, and those leaders are the conduit through which they serve the RBSO. A corollary to that point is that what the Rebbe says is law from the RBSO, similar to as if a Navi said it.
Everything DY said is true as well to some extent. There are many adult male Chassidim who interact with the outside much more than Litvaks or Yerushalmis (for example, Satmar).