If you tend to get bored with foods relatively easily, then I think the 4-day diet would probably be good for you. They both work well but the 4-day is broken into modules that you only follow for 4-days at a time and the foods keep changing. There is a lot more exercise involved with the 4-day which I think is a good thing too. Good luck with your choice! I'm on day 2 of the 4 day after doing the FS and this is MUCH better for me.