Discuss the advantages and disadvantages
What's then? 4 or 5 paragraphs?
Well, if you have a question that you don't like at all, then you can write with a 5-paragraph essay. You write one introduction, three bodies, and one conclusion. This can help you write more words, but some seems inefficient, by writing too many words.
With a 4-paragraph essay, you are easy to develop your paragraph properly, one content paragraph for advantages, and one for disadvantages. This is good for coherence and cohesion between sentence to sentence and paragraph to paragraph, and for which in the five-paragraph structure this is weak.