| Purdue is undoubtedly the strongest of the three for business (and probably overall academically), but you also have to decide how happy your son will be living in West Lafayette, since it is fairly remote--with not a ton of things to do other than what Purdue provides. My son was accepted to Purdue, but just decided it was a bit too "slow-paced" for his liking, and so is attending Indiana University at Bloomington instead.
On the other hand, Tucson (Univ of Arizona), and Waco (Baylor) aren't exactly the busiest cities either. Also, weather plays a role. It will be a lot colder during the school year (during the days) at Purdue as opposed to at either Arizona or Baylor.
I think I'd choose Purdue first, then Arizona, then Baylor--but they are all pretty good schools--and Baylor is well-known for its excellent medical programs, and Arizona for some of its science programs (and Purdue for engineering, of course).
Good luck to your son with his decision. | 
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