Form as defined by the reader.

Open form and closed form prose are basically a matter of style. I would imagine that most writers prefer one over the other based on their taste and personality. The difference is pretty simple, closed form implies a professional and non-personal voice whereas open form seems to often be conversational, creative, and fun. However much a writer might like one or the other there will be times when he/she chooses the other or a mixture of the two simply because the audience a certain piece is aimed at requires a more or less formal style. Any piece that is to be successful needs to consistently remember to compare itself with the needs of the audience and if it meets those needs adequately then it will almost always be a success.