Personally, I would go with school B. You don't have to worry about money (which is a concern for me, but may not be as much for others), you'll have the advantage of a small cohort which will hopefully manifest with a lot of personal attention from faculty and more funding for travel, and having three profs there with similar interests means that you get support and guidance for your research, but you also will have the benefit of differing perspectives. And, if one leaves or goes on sabbatical, you have the other two as backups.