How does Laertes's advice differ from Polonius's?

One of the most interesting things about Hamlet's Act 1, Scene 3 is how the loving brother, Laertes, is contrasted with his own father, the foolish Polonius. Another bit of irony is that they are proven as such through their words of advice. Laertes, who is about to go abroad, issues some bold (though possibly hypocritical) advice to his sister, Ophelia. These words of advice center upon Hamlet's possible love for her. Laertes, doesn't want Ophelia to concentrate on Hamlet's advances and love. Above all, Laertes reminds Ophelia of the importance of her virtue. Perhaps his most important words of advice center around the fact that "for [Hamlet] himself is subject to his birth."
Then, literally twelve lines later, Polonius shares his advice for his son. Polonius is immediately cemented as a fool by instructing Laertes, "Aboard, aboard, for shame!" Polonius spits cliches, and in so doing, doesn't make a single one seem of any importance. This conversation serves to initiate Polonius as the fool of the play. Ironically, some of these cliches become the most memorable allusions to Hamlet found in our modern world, such as "neither a borrower or a lender be" and "This above all, to thine own self be true." Unfortunately, if you read between the lines of Polonius's own words of advice, you find nothing more than copied aphorisms. True wisdom is found elsewhere.