This is a big decision, based on time, commitment and finances. From what I have heard, GA-Pre-K is geared towards children who have not had ANY exposure to any type of preschool, children's TV programming, reading/basic skills, etc.... There are some excellent private pre-K, including may church-affiliated programs that benefit by offering small classes and excellent teachers.
As a note, when children enter kindergarten, they are on a fast-track to learn how to read and much is expected from them, as well as their parents, in terms of homework. As the other poster has commented, the success of your child as a student will greatly depend on the educational guidelines estabilished at home and involved, dedicated teachers.