I haven't used them yet (baby due in July), but I do have one or two of each. Like the pp said, the 3.0's are pocket diapers and you have to stuff them for use and unstuff for washing. The advantage is they dry quicker that way and they are one-size so theoretically they should work from birth to PT. The AIO's don't need to be stuffed but take a long time to dry and you need different sizes as your baby grows. Both of these options come in velcro, which can wear out I guess. BG also has an organic, one-size all-in-one that comes in snaps. It is quite a bit more expensive, but I got one with a coupon b/c I was curious and it looks really nice and I like the idea of snaps.
Right now there is a coupon for a free BG AIO with a $10 BG purchase in a couple of parenting magazines. You can check out details on
momsmilkboutique.com , under sales and specials - they will clip the coupon for you and they have free shipping on everything, so that might be a good deal if you want to check them out.
HTH!