STLC / SDLC
Its like asking which had is Better ! Right Hand or Left Hand and if there is difference between them.
as said, it depends on the purpose, if you can do it with your right hand or if your required to do only with your right hand then use the right hand only.
alternatively, if there is no boundaries on using both hands then always use both the hands, it gives you an advantage.
so if its only SDLC that is required or if inly STLC is required, used only what is prescribed, else use SDLC and STLC and it gives you the advantage of both of them