I certainly agree that the decision is more difficult for pitchers than position players because of the coaching, overuse and care concerns. Serious research is required on the school selected.
Alas, no such research is available for the draft; the player doesn't have control over who drafts him and some organizations are considerably better than others on care and coaching. Overuse isn't so much of an issue in the early days; they've got too many guys to look at and I haven't heard of any without pitch counts.
You know your son and his maturity level. In MiLB, he will be called upon to be an adult; in college, he has (as has been stated) a support system to guide him in academics, rest, workouts, and getting fed. Do not underestimate the value of getting fed until you've lived on clubhouse ham sandwiches for three months.
His 'social life' will be the team he's assigned to. (OK, and the Annies if he's so inclined.) And, as has been mentioned, a number of them won't speak English. There will be politics to play.
On some teams, he will have to find accommodation which may or may not be convenient to the field. He may well have a car, but that may become immaterial when he changes teams at a moment's notice and Mom or Dad is called upon to fly to the old team to drive said car to the new team or home.
HS students have rarely been away from home for extended periods of time. Consider how that will affect him. Yes, they would be away at college as well, but with a broader range of activities and holidays and breaks every few months. MiLB will be as much as 4 months the first year, then at least 7 in subsequent years.
MiLB is baseball and only baseball, which may sound like heaven.....but so does eating nothing but ice cream.
5% of all MiLB players see a day in the Majors; 3% will have a career. College is a better preparation for life for the 95% who won't have a career.
If he is injured in college, he may never get to play pro. If he is one of the 95%, will he go back to college? The MLB scholarship numbers indicate he won't, but you know your son on that count. Somebody said college at 18 is different from college at 26. That, however, may be overestimated as that suggests he'd be playing for 8 years --- so don't get lost on that number.
But if he's good enough to be considered a high draft pick out of hs, chances are he will be out of college. And you can make this decision in his junior year, when he'd be looking at only one year to complete should he need to.