A bit bemused that the choice for a student who has anxiety issues and is worried about a competitive atmosphere has narrowed the choice to JHU & Cornell- two schools that are heavily stereotyped as full of competitive, highly stressed, overworked, unhappy students.
Most of the concerns that you have mentioned above are second or third tier things: weather isn’t what makes a school work or not work (and Baltimore, while definitely not as cold as Ithaca, is no great shakes for weather either anyway). “Cornell/Ivy League” vs JHU is about the bumper sticker on your car, not something that will meaningfully advantage/disadvantage the student. Ithaca is farther from cities in absolute terms, but for the lived student experience is arguably less isolated than JHU, as the students free range through both the town and the region. NYC isn’t a day trip, but it’s easy enough to take the Cornell bus for the weekend, similar to Baltimore (yes, I know DC is an hour for JHU away also).
Your point that he is not 100% sure about engineering seems relevant to me, and would tip the balance a bit towards Cornells encouragement to take a range of classes.
Still, the bottom line is that both places are chock-a-block with students who take their work very seriously, and who push themselves. Neither is what I would imagine is an obvious fit for a kid who ‘suffers from high anxiety’ about exams and academics.
If those are the only 2 choices, then I would go with the place that he felt more comfortable.