Yes you are lucky that you have very good choices in top schools of similar size with students who tend to really love their school. It may not really matter where you go. People tend to like where they choose and take advantages of the opportunities they find where they are. While you think you are making decisions based on every little thing I don’t find your reasoning very sound, and I think you may be coming at this with the wrong attitude. If you are thinking that Brown is going to be easy and not have very strong science students or programs you are mistaken. Neuroscience is a top program at Brown as are other sciences and applied math and CS are very strong and student come to Brown specifically for those programs. So while you may not stand out as the best student in your class there are many ways to make your mark, many opportunities for research with faculty , opportunities for university grants for research.
As far as resources I don’t get what you mean. Brown does have a smaller endowment than Duke but I don’t know what spending per student is or how it will affect you personally. In the last decade Brown received two 100 million dollar donations for the college and the medical school. They built a brand new Sidney Frank Life Sciences Building on campus with 60 labs. They have the interdisciplinary Brain Research Institute on campus headed by Nobel Laureate Leon Cooper. The med school has 7 affiliated teaching hospitals in Providence. Downtown Providence is 3 minutes by car or 15 minute walk to the medical school. But Brown has a defined campus feel by being across the river on College Hill.
Yes Brown is very much noted for a collaborative atmosphere which is something my daughter has remarked on, the way the departments work and the atmosphere of the student body. Particularly when she was looking at grad schools and noted the differences when visiting programs she was accepted to. Good luck with your decision and please continue to discuss if you have more thoughts.