OP, Harvard is the no-brainer. In my mind, I can think of three obvious reasons:
(1) For someone interested in the social sciences/humanities, where something along the lines of a "professional sociologist" is rare, Harvard gives a lot of versatility for future job prospects because college can easily change a 17-year-old mind. Firms like McKinsey, Goldman, et al. throw state school applicants' resumes in the trash while they wine and dine Harvard students.
(2) Even if you're absolutely dead set on law school, having work experience after college really helps in the admissions process, and working in prestigious firms significantly adds to it. It's one of the reasons for example Yale Law's student body undergrad make up is 30% HYP and 50% Ivy.
(3) State school is not as easy as you think. With the larger pool of students to compete with, "real" grading curves, and the large numbers of I-don't-give-a-$hit-about-teaching faculty, you may end up with a lower GPA -- not because of intellectual reasons, but simple logistical reasons, which is even more frustrating. Of course, this is variable depending on the school you go to, but even top-notch ones like Cal or UCLA have many of those negative factors that a Harvard undergraduate avoids.
Sorry if this post sounded elitist, I'm sure it must have, lol, but I'm just sharing from personal experience. PM me if you want more details.