I'm not a student, but I have read tons of posts on this topic. Seems to me like there are 2 important things:
1. Every school ranks their students so that they have a way to present students in deans letters to residencies (except a handful, and this is being phased out supposedly), so either way you are going to have a rank. The only difference between p/f and a/b/c/d is that you will have a letter grade assigned to it. You are still 'competing' for your spot on the ranking list
2. If you are a person who would be stressed if they saw a C or B rather than a Pass (even if the grade is a 75 or 80), maybe it isn't for you. But if it's the only thing holding you back, I heard you get over it quickly anyways.
General consensus is that every single school will tell you that their students are non-competitive and very collegial and blah blah. Of course there are always the few that aren't.
Hope that helps