The benefit of smooth implants is that they can typically be placed through a smaller incision than textured implants. They also tend to have a little softer feel after the augmentation as the implant will have a little movement in the pocket giving it a natural appearance and feel.
In the end they are both great implants depending on your particular situation both implants have their place in breast implants surgery.
Please discuss your breast implant surgery with your board certified plastic surgeon who can help guide you and help you achieve your aesthetic goals.