If you go to HLS, you're guaranteed a biglaw job. As good as Duke is, if you're at the bottom of your class, you're not.
Also, you will in fact always be able to impress people, employers, clients, etc. to some extent with your Harvard pedigree. Everyone around the world knows Harvard. Many people in the midwest know Duke only as an effeminate basketball team.
When it comes to partnership opportunities, assignments, etc., many Harvard partners will favor other Harvard grads, even over other top schools. Some firms (though rare) will ONLY hire Harvard grads.
And obviously, if you want to teach, either in law school or college, it will help.
That doesn't mean you can't screw up your career even if you come from Harvard -- I know harvard people doing document review. But it's harder to do so, and usually results more from self-selection.
Bottom line -- given that you're guaranteed a biglaw job, and have those other benefits, I'd definitely take HYS over a full-ride at many T14 schools. (Yale would be even better in many ways, of course.) If I was offered a full-ride at CCN, or even MV, I'd have to consider it, because those schools have more comparable traditional reputations. But many would of course turn down even a full ride from Chicago or Columbia because of those benefits.
(Others, more self-driven, bottom-line focused, and self-confident of their own hustling and professional abilities would of course take the full-ride at any top 14/20 school.)
All things being equal lets shift the focus from Duke to a full ride at Columbia or Chicago vs. Harvard. What then? The 160K in cost just doesn't seem to be worth a full ride at a comparable school. No offense. I understand the academia point, but I think that only applies to those who wanna teach at another T14. I think the majority of law schools would be ecstatic to have faculty from columbia or chicago otherwise.