Hey, it's me. said:
Both. You can't differentiate between the two. Plus a decent script and and a director who knows how to tell a story. (Irwin Kershner springs to mind)
Kershner is dead though. The screenwriter Lawrence Kasdan is very much alive and working as a consultant on the sequel trilogy.
George Lucas is also alive if they need to ask any questions about the universe. Characters, background etc, as Kersh and Marquand were able to approach him for input.