The article says "some would say that prose is more difficult to write effectively" but I disagree. I think that poetry is much more difficult to write for a couple of reasons. One is that you generally have to follow a rhyming pattern (although the article correctly points out that not all poetry follows a specific rhyme scheme). The second is that poetry in general seems to be more abstract than prose writing. I consider myself fairly well-read, at least in terms of prose, and almost always pick up pretty quickly on what's being said. But poetry, for some reason, tends to baffle me. I often have to read a section or a stanza a couple of times to parse it out.