The Be Prepared is pretty huge. I have one and I use it to hold clothes for me and DD when we go out of town for the weekend. It's that big. If you are truly an overpacker and are packing stuff for all day, it would be okay, but for anything more than that it might be overkill.
It also gets heavy if you plan to carry it all day. The BFF is a more manageable size. Don't get me wrong, both are great bags, but the Be Prepared is really big. There are packed pics on JJB's Pink Room if you want to check out how much it holds and how it looks when worn.