Springtrap is possessed by purple guy and I wouldn't trust spring trap ever again. GF is a victim(as a child) of death by the purple guy.
Golden Freddy is a Ghost, so SpringTrap couldn't touch him.
Springtrap and Golden Freddy are essentially the same thing. Springtrap is better because it still has the spring trap.
ill agree with what immortalvoddler said, as they are basically the same animatronic, however, springtrap possesses the ability to move, unlike golden Freddy, however i like freddy's design much better as it is less decayed and more creepy