From my reading, the abdominal binder is to help support your stomach muscles while you heal. I remember not wanting to cough or laugh after having my babies because it hurt! I know they're recommended for C-section mamas because they have even more muscle weakness from being cut. I know belly binding is really common in some cultures.
The hip binder is supposed to be good since your joints are so loose after baby. But I'll freely admit that part of it appeals to me because of the shrinkage claims, lol! The name brand hip binder sites say that if you wear it for 8 weeks postpartum, it will hold your hips tight until the relaxin leaves your system at which time, your joints are solidified into a smaller position. So, that mama hip spread is supposed to be better if you use the product. I'm totally sucked in!
And then, the rib binder just made me laugh because a friend of mine was bemoaning how pregnancy had left her ribs permanently flared. I don't really have that problem, but if you do, you might like it ;)