The different levels correspond mainly with the strategic level that you are operating at. So, for example, a level 3 qualification will focus more on the basics of operational, day-to-day FM, whereas the level 6 focuses more on setting and delivering long-term FM strategies and making sure that the FM department is aligned with and supportive of the overall business strategy.
Although we do teach about the importance of strategic thinking and seeing the bigger picture across all of the levels, it becomes more important the higher up you go when it comes to both completing the assignments and applying your knowledge to your role.