New Oxford Dictionary of English says
Pitcher, Brit., a large earthenware container with one or two handles and a lip, for holding liquids
Jug a small or medium-sized cylindrical container with a handle and a lip, used for holding and pouring liquids
Seems to be a size thing over here.
Merriam-Webster's says
Jug, a) chiefly British, a small pitcher, b) a large, deep usually earthenware or glass container with a narrow mouth and a handle
Pitcher, a container for holding and pouring liquids that usually has a lip or spout and a handle