In the Banquet Speech Dylan mentions that he never asked himself if his songs are literature. In his own words: "Not once have I ever had the time to ask myself, "Are my songs literature?""
In the Lecture he's wondering exactly how his songs related to literature. In other words the big question is if his songs may be called literature.
In both speeches he seems to compare himself to Shakespeare. It may seem immodest to do such a thing, Shakespeare's plays being widely accepted as literature. But what he's really saying is not 'I'm just as good as Shakespeare' or 'Who’s best, Shakespeare or me?'.
After having mentioned in his lecture a few literary masterpieces that have meant a lot to him and have inspired ham all along, he gets to the point. And the point is that Shakespeare probably didn’t think of his writings as literature. In Dylan's own words:
"The thought that he was writing literature couldn't have entered his head. His words were written for the stage. Meant to be spoken not read. When he was writing Hamlet, I'm sure he was thinking about a lot of different things: "Who're the right actors for these roles?" "How should this be staged?" "Do I really want to set this in Denmark?" His creative vision and ambitions were no doubt at the forefront of his mind, but there were also more mundane matters to consider and deal with. "Is the financing in place?" "Are there enough good seats for my patrons?" "Where am I going to get a human skull?" I would bet that the farthest thing from Shakespeare's mind was the question "Is this literature?"
Likewise, he says, "I too am often occupied with the pursuit of my creative endeavors and dealing with all aspects of life's mundane matters. "Who are the best musicians for these songs?" "Am I recording in the right studio?" "Is this song in the right key?" Some things never change, even in 400 years. Not once have I ever had the time to ask myself, "Are my songs literature?””
So that's the intention of dragging Shakespeare into it: Neither have thought of his work as literature.
Bob Dylan concludes with a line from Homer: "Sing in me, oh Muse, and through me tell the story."