I've spent time in Boston and it earns its reputation as a cold east coast city. I don't know why, but people seem uptight and unfriendly there.

Baltimore is extremely welcoming. People say "hey" to you on the street here.

If I were trying to choose between JHU and Harvard I would talk to some people at both universities. How happy they are will say more to what you can expect at each place than what a bunch of reddit weirdos like me have to offer. The answer will almost certainly depend on the culture of the program at each.