Back three vs back four: What are the main differences between the two systems?

From a tactical perspective, this may be the biggest difference between football teams: the number of players forming the back line. It affects the shape of the entire team, the style of play and the strategy. A host of systems have been used throughout history, but in the modern game, the three-man and four-man defensive models are competing with each other. Which one is more effective? The new Flashscore series seeks to answer that question, regularly analysing trends and developments in world football with the help of data.