I have also gotten accepted to both schools, so I understand the dilemma. I've decided to go to Duke (if I don't get into Stanford). I'm Out of State by the way, (Arizona), and I didn't read if you were in or out of state but the price issue might affect your decision if you're in the California school system.
I think Duke is better because I believe that at Berkley there is purely a "nerdy" criteria to gain admission but at Duke there is more of this pervasive all-around "well-rounded" student body. Duke seems more to me like a school to develop the whole person, as opposed to strictly academics.
UC Berkley is also a lot larger than Duke, which means less-intimate professors and class size. I think that overall Duke is a better atmosphere, but of course, this is mainly personal opinion. You can find all sorts of opinions on the issue all over the web, (this website in particular), but when it comes down to it, the schools have extremely different atmospheres, but similar academic excellence.
You'd do great at both.
