I'm mostly deciding between Convoy (a YC company that is growing really fast) and Flatiron Health (got acquired by Roche earlier this year but is an independent subsidiary). The Flatiron internship is in New York, has great perks/training bootcamp, is really generous, and they're working on an important problem. The main thing going for Convoy is they are still private and are growing crazy fast. How important is the growth of a company you are interning at compared to other factors, like having a more established process/location/pay/training programs and focus on internships.

For a little more context, I'm not too concerned with getting a job after the internship and I worked at Intel last summer (so it would be my second internship).

Thanks for your comments!