If it were me, it would come down to what you value more and also the impact those decisions would have on your future. So I see it as a problem that needs to be broken down into smaller problems. Based on your descriptions, I think those problems could be broken down into personal, education, and future. And from here, I'd try to weigh which of these 3 categories you value ranked from 1-3. If personal factors are ranked 1, then school A would likely be my choice. It'll allow you to foster the right environment for you to not only be successful in the classroom and out of the classroom. You'll likely feel less personal stress, which as you know, will allow you more ability to be stressed in the classroom (lol). Now, if you care more about the content of the education and how it relates and reflects your areas of interest, then school B would be the better choice as you will likely feel more comfortable with the subject matter, faculty, and overall confidence in your abilities to be successful. I'd say future is the wildcard. Despite what anyone tells you, sometimes going to the more prestigious university will have potential at opening up more doors, new opportunities, or even getting yourself published in the top journals in your field. If these two universities are equal in caliber, then this is obviously not a concern for you.
At the end of the day, I'd always try to break a major problem into smaller problems, however you decide to separate it. And if all else fails, go with your gut. Never change an answer on your test, and never change an answer on your gut decisions.
Good luck, hope that helps.