At the very least it would have been more like an Indy film because George could produce Steven but not try and over the shoulder direct/second guess in the manner that is continually suggested he did/tried to do with Richard Marquand.
Ironically Spielberg had just finished Poltergeist where it is strongly felt he did this with Tobe Hooper and ghost directed much of the film himself.

I’m sure Spielberg would have insisted on rewrites and the film would have been stronger because George would have felt he had to listen to him. But it also would have had a Spielberg flavor which is alien to the Star wars universe too.

Weirdest of all is that this could have been directed by David Lynch.