I was applying to both, but after I got into SSP and saw the aid package they were going to give me (plus, I’d been to Stanford and wanted to live on the east coast for a few weeks) I didn’t finish my application to Stanford.

I definitely had one of the best times of my life there, taking a class that was fascinating, doing whatever I wanted, and just having fun (note: that I consider my class fun, as I did spend a considerable amount of time doing something I loved).

I think you should find the course lists for both programs, and pick out all of the courses you would take, and prioritize them based on your interest. I would apply to both unless one school doesn’t have any classes that you wanted to take. As for deciding, if you get into both of them (I recommend applying early, so you get accepted early, so the classes are wide open), think about where you would rather go.

Stanford and Harvard have extremely different campuses. Stanford has a large, open, campus and is situated on the West Coast (lots and lots of sun). While Harvard is situated on the East Coast (cold, snowy winters!) and is much more urban (read: thousands of tourists daily). I personally like Harvard’s campus better, I loved my dorm, my classroom, pretty much everything about it.

So, my priority was:

1. Classes I really wanted to take
2. Where I would have a better or new experience (campus-wise and city-wise. I’m familiar with Silicon Valley, not so much Boston).
3. Climate

Good luck. I hope you find a program that you enjoy.

To add to this, I think both would provide a great experience for the subjects you are interested in. They are both two of the world’s best Universities. If I was to make my decision purely off a ranking system (such as QS) they would be positioned as follows:

Maths
Harvard is ranked #2 in the World, Stanford is ranked #4=

Chemistry
Harvard is ranked #4 in the World, Stanford is ranked #5

Biology
Harvard is ranked #1 in the World, Stanford is ranked #5

It’s important to note the QS is just one of many rankings, and should not be what you make your decision off. What I’m trying to say is that no matter where you go, you’ll love the classes that are available.

Make your decision based around the location you want to be in. Both will provide exceptional experiences nonetheless.

I hope I helped