I love Columbia but I would say to take the BS/MD if it will allow you to enjoy college. Getting a 3.5 GPA is definitely something you could reasonably expect to achieve at Columbia but the stress would be real. Essentially every class is curved so you not only have to be smart but you also have to be willing to work harder to get As which then impacts on social life and extra curricular opportunities. If you really need to have a 3.8 gpa that will be stressful plus usually pre meds need to do research (very competitive to get these jobs in pre med at Columbia) and some type of med shadowing/volunteering. It really comes down to if you would be happy with Kimmel and if so then you should probably go with PSU especially since you mention stress as a decision factor.