"There isn't" vs "There is no"

(Grammar Questions I Couldn't Answer)

This time the question comes not from a student, but from a teaching-colleague, albeit one whose first language wasn't English.

He asked me if I would say: "There isn't a sofa in the living room" or "There is no sofa in the living room."

I told him both sentences were grammatically correct.  But put on the spot, I couldn't decide which one sounded more natural to me.

Once upon a time, I might have been tempted to tell him that they were exactly the same.  But after reading Michael Lewis, my thinking has changed on the subject.
Michael Lewis argues that there are no exact synonyms in grammar.  Different grammatical structures imply, if not different meanings, at least a change of emphasis.

I puzzled over these two sentences to try to figure out what the difference in emphasis was, but couldn't figure anything out.