I do not know how strong your student is academically and emotionally. But assuming he has a strong disposition I’d choose Purdue.
If y’all are worried about meeting the standard academically for continuing into the engineering major or you think there is at least a 50% chance he will change majors to something non engineering, be sure the school he is considering has a range of majors that are strong or good in the fields he may likely be attracted too (I am sure all of the schools would likely have thus covered, but it doesnt hurt to do some more research!).
As @ucbalumnus pointed out, I might reconsider Pitt…but I can see that Purdue and Penn State are more similar in other ways than what you have with Pitt and why Pitt may have fallen in the choice.
I think he will find the freshman “weed out” classes pretty similar across the board. No school on your list is really going to be any “easier” than another. Freshman year engineering (really any year engineering) is going to be tough.