Money has nothing to do with it except the court fees are �30 less for SGO than residency. I doubt you parents will be thinking of money as they embark on a future looking after your offspring into their retirement which they had not planned for.
The difference is that the parents still have Parental Responsibility, but the person who has the Special Guardianship has overiding PR.
It means that you would have to apply for leave of the courts before applying for the child/ren back and would have to prove a significant change in lifestyle. It applies until the child is 18 and that your parents can remove her from the country for 60 days rather than days without your permission.