The major advantage of a compressed work week is that it gives workers more flexibility. When workers work a compressed schedule, they are typically able to work four days a week instead of five. This means that they will be able to have an extra day that they can use if they have personal responsibilities or if it is otherwise helpful to their families. It also means that they do not have to commute as many days. For the employer, it might allow more customer service for longer periods. Instead of having important staff leave at 5:00 every day, some of them might stay until 7:00. The employer might also benefit from having employees with higher morale.
For the worker, the main disadvantage of having such a workweek is that the days that they do work are longer. They might be more tired and run down by the end of such days. For the employer, the most likely drawback will be that there will be days when some personnel are missing. On those days, it may be more difficult for things to be done efficiently because the full staff will not be present.