Take out loans?

Hi all, I have a question about taking out loans vs paying for school upfront. Basically, my boyfriend has a savings account that he intends to use to pay for medical school. He starts this fall as an MS-1. He received about 50,000/year in aid, and his COA is at nearly 100,000 per year (about 69,000 in direct tuition and fees and 30,000 for other expenses in a big city), so his out of pocket cost will be about 50,000 per year (20,000 to school and 30,000 for living - obviously less if possible). If he took out loans, it would be near 200,000 over 4 years.

Basically, he has 1 large sum of cash coming his way from a family member who saved for him. His question to me, and my question to all of you, is, would it be smarter to take out loans at a lower interest rate than he could get on, say, an index fund? I was trying to think of the major pros and cons of loans vs. no loans. For me personally, the loans are hopefully not such a big deal - I have near 500,000 from undergraduate, med school, and a joint degree - because I am working at a non for profit and intend on using PSLF (I have 6 years if training ahead of me). I am thinking that, for me personally, I'd rather have the loans to pay off if it meant also having 200,000+ in the bank for a house or something. What do you all think? Is 200,000 enough of a loan that PSLF makes sense and keeping the cash is worth it considering the potential for a higher interest rate on the cash than on the loan?