So figure out what you care about in a college - location, size, reputation, athletics, whatever - and choose between these vastly different institutions based on that. If the premed opportunity is part of that calculus for you, fine - but if that's your only consideration you won't be doing yourself any favors.
HanginInThere is so right about it all. I also graduated from Dartmouth (was pre-med there) and just finished applying to med schools this year. Couple things to add:
-I absolutely LOVED my dartmouth experience and couldn't imagine myself loving another college more. That said, it's not for everyone. I grew up in a city and like cities but didn't want to go to college classes on the 12th floor of some building downtown. I wanted the ivy covered (i mean the plant, not the group) CAMPUS feel with historic old buildings. New England is BEAUTIFUL (I grew up in AZ) and it was so much fun to live in 4 seasons. I loved being able to go for runs in the fall, ski after class in the winter, and float down the CT river in the summer. Winters get cold but they're not deadly and it's a badge of pride to live through them and be ok. You'll buy a good coat and be fine. When you visit, just talk to AS MANY people as you can and ask why they like/don't like dmouth...my host actually hated Dartmouth so it was good I talked to others. Dmouth kids are def a work hard, play hard culture and it was a great environment for both. Dmouth is pretty much ONLY focused on its undergrads and is known for its undergrad name (I'd say USC has a better name for med school than undergrad). And yes Hanover is a small town but people forget that 4000 of your friends are living in the same town as you. You end up hanging out with friends in apts, having house parties, or doing other random cool things. I have the rest of my 20s to go to bars in cities and see shows and whatever and didn't really miss that for four years as long as I had all my best friends around. Also, the Dplan is really unique so learn about it when you're there and look at some student's sample Dplans. It gives you the opportunity to do some really cool stuff as an undergrad that most people can't get till med school (I had 4 months of international medical experiences on my app for med school that med schools were pretty impressed with).
-Premed at Dartmouth: it pretty much sucks but what's important is that I don't think it sucks more than anywhere else. You're going to take hard classes with lots of labs and in general work more than your anthropology majoring friends. The benefits of premed at dmouth is that dmouth is small so you can REALLY know your profs and use them for help like at very few other schools. I really dont know much about USC and have friends that liked it there but dmouth is personal. The biggest premed class you'll take is gen chem at 100-150 students. A negative is that there's not a great premed advising support system in place but it didn't really matter to me because classes were so small that I could always get help/advice from profs and upperclassmen that I knew.
-Dmouth's name: I don't think it terribly helped me or hurt me in the med school app process. Go to either school because you like the very different characteristics of each, not really for the name. A 3.8 from either school will get you very far. It's getting the 3.8 that's hard at either school.
-Extracurriculars: In reflection, I think my app was hurt because I had too MANY ECs, most all of them medically related. So those of you that have never been to Hanover, please don't comment on the availability of med related ECs. DHMC (dartmouth's hospital) is an AMAZING huge place that sees every referral case for 4 states north of Boston which means you do get to see a lot if you shadow/volunteer there which a lot of premeds can easily do. It's also SUPER easy to start researching your freshman fall at the hospital, med school (which is on the same campus as undergrads with a lot of overlapping profs), or undergrad campus which you can't necessarily do at other bigger schools. There's a TON of international health opportunities. Also, most of my friends coming out of Dmouth who did great in the app process had mostly non-med related ECs that they loved and could talk about with passion so that's something too.
My advice is just look at what your EXPERIENCE will be like at both schools b/c i'm sure it will be pretty different (and not bad at either school). Ask yourself what you want. I'm not gonna lie, the auto accept to USC med is great but if you're motivated, you can have a great undergrad experience at Dmouth and then go to a great med school of your choice. Really talk to PEOPLE (profs, students, etc) at both schools...are they cool? Are they people you want to be friends with and hang out with for four years? And stay open too once you get to college - be a biochem major if you really love it but if you love history or whatever, major in that and kick ***. Try some non-med ECs too...med schools want you committed to a couple great ECs, even if they're not all med related.
Good luck with the choice! I'm sure you'll make a great decision whichever way you go and have a fun four years (let's face it...college is great). Feel free to PM (personal message) me if you have more questions about Dmouth or anything.