Deciding between Harvard SEAS and Princeton for grad school

I have two days (until Monday) to decide on a grad school in physics. I visited Harvard and really liked the city, but the research groups were all huge (20-30 grad + postdocs was common), and it is quite hard to work with an advisor outside of SEAS. I am not at all sure which field I want to do research in, but the research at Princeton appealed to me more. The only thing I'm worried about at Princeton is that I've heard it's more undergrad focused and grad life can be isolating. Then again I think I could make do if I found a research group I really liked and took semi-regular trips to NYC. If you have any advice or thoughts on this I would really appreciate it!