I have them in all the sizes from Mini to Desk. IMHO, it depends on your needs. I use my mini for CC cards and a tiny address book from WAY back in the day before I could save that kind of stuff on my phone. The PM I use for my personal meditating/grateful/spritual type journal. The MM is in my purse and runs my life, lol. Without it, I am lost. The GM I use for my business (we own a few rental properties and I manage them) as well as anything to do with those properties (taxes, HOA's, vendors, etc). The Desk is a copy of my MM but left at home on my desk so all members of my family can check it for important dates (travel, Dr. appointments, exams, school days off, etc). For me, the planners keep everything seperate (that need to be kept seperate) and organized.