I’m torn between deciding upon UMass, Amherst and JHU for PhD in CS specializing in AI and Vision.
Leaving the fit of lab aside, which of the two fairs better in -
I wouldn’t set fit of the lab aside, though, as that can outweigh some of the other factors on your list.
I will preface this by saying I am not in computer science. That said, have you been to CS Rankings? Leaving the entire AI area on seems to indicate that UMass-Amherst (at #11) ranks higher than Johns Hopkins (#23). That remains true if you narrow it down to just artificial intelligence and computer vision. It does change, however, if you look at one or the other. In computer vision alone, JHU ranks #13, while UMass ranks #24. In artificial intelligence alone, UMass is ranked #6 and JHU is ranked #50. (If you look at computer science as a whole field, UMass ranks #22 and Johns Hopkins ranks #43.)
The National Research Council also performed a ranking of doctoral programs in different fields (although it is nearly 10 years old at this point). In the NRC’s ranking, UMass is #18 and JHU is #37. You can see both their absolute ranking and the average of their scores on the methodology the NRC uses here (http://hpdic.cse.unr.edu/download/NRC_Ranking_in_Computer_Science.html) and see different kinds of rankings (research, students, diversity) at the Chronicle of Higher Education here (https://www.chronicle.com/article/NRC-Rankings-Overview-/124721).
Indications seem to point to UMass being overall higher-ranked in the general area of AI, although JHU may do computer vision more. I’d say that overall, it appears that UMass’s reputation in CS is better than JHU’s, but not by an astronomical amount. The difference probably matters more in academia than it would in industry.
As for graduate hiring and where alumni go - that’s a question you can ask the department. You can ask them about placement information both within and without academia. However, five years ago some scientists wanted to analyze the role of institutional prestige in faculty placements, and one of the fields they analyzed is computer science. You can read the paper here:https://advances.sciencemag.org/content/1/1/e1400005
Essentially, they found that the top 15% of programs produce the vast majority of faculty in three very disparate fields (including CS). Fig. 4 shows that UMass places their students relatively well - perhaps not as well as Stanford (which is #1 and presented right next to them), but still pretty well at mostly prestigious institutions. JHU’s network analysis would probably look closer to Colorado’s.
One thing to keep in mind, though, is that a weird quirk of elite universities is that they attend to attract a lot of top companies who are there after their undergrads who also may pay attention to graduate students (or where, at least, graduate students can take advantage of career fairs and company visits). This is not necessarily a good reason to choose JHU over UMass, but it is likely true that there are more top tech companies visiting JHU in an average year than UMass.
Environment - well, that totally depends on you and what you like. Amherst is sleepier location for sure, more a small college town than anything else. You’ll be outnumbered by the undergraduates given the Five Colleges. It’s likely to be very quiet during the summers. Amherst, and the Pioneer Valley in general, has a reputation as an excellent place to live - it’s not called “Happy Valley” for nothing. But if you’re a person who prefers a large urban environment, that might not be a good fit for you. Boston is two hours away, which isn’t terribly far but probably too far for spontaneous evening hops into the city. Hartford’s an hour south, but that’s a small city. And you have to drive to both (or take a Greyhound).
JHU is in Baltimore, which is a fairly major U.S. city, a short distance to DC (a distance that is easily closed by public transit). You’ll have all the pleasures and the downsides to a large metropolitan area. Crime in Baltimore (including violent crime) is above the national average and has been for a long time; however, most of this crime is concentrated in a small percentage of high-poverty neighborhoods. You have the entire Northeast Corridor within easy reach - 2 hours to Philadelphia, 3-4 hours to New York, and train lines are easy so you wouldn’t have to drive.