Howard Greene wrote a book called Inside the Top Colleges. http://www.amazon.com/Greenes-Guides-Educational-Planning-Realities/dp/0060929944 It’s a bit out of date now, but I suspect it’s still pretty accurate. He surveyed students at a number of top colleges. One question he asked was something like “Do you consider your classmates cutthroat?” If I remember correctly–it’s been a while–there was no college at which the majority of students said yes. However, the percentage of yes answers varied from about 40% at Johns Hopkins, the highest, to zero% at Wesleyan and one half of one percent at Brown.
You might want to see if you can find the book in a library; the relevant section is just a couple of pages. Again, while the survey is pretty old now, I think the underlying “personality” of colleges changes slowly and the book might give you a starting place.