I think all the advice already given to your question are valid reasons student-athletes might select a JUCO. I'll just throw in my "two-cents worth" because my son has been at two JUCO's in 2 years, and I think that players and their parents need to know all aspects of their decision to go the JUCO route.
If your kid wants to go JUCO and he is a "Draft and follow" in a middle to low rounds, this makes good sense. This allows the scouts to watch him play for a year, and if he does well by making a significant impact on his JUCO team, his MLB team might offer him a better signing bonus than his initial draft round would normally bring.
However, if your son is not a "draft and follow", it would be wise to find out if the other kids vying for your son's position are "D and Fs", because very likely the kid who has been drafted will get a more serious look over your kid. I'm not saying that the drafted kid always wins out, because if your son is as good or better, he will get some playing time...I'm just saying that the chances are likely that the drafted kid will probably play, and may even get the starting spot because it's a win-win situation for the JUCO club----the drafted kid brings credibility to the JUCO club for that year, he brings the scouts out, the scouts are expecting to see the kid play, so in turn, the coach will usually put him out there, and if at the end of the JUCO playing season, the MLB club chooses to sign the drafted player for a better signing bonus, this is a really big "feather" in the coach's cap because then he can rave about the kids who sign out of his program. It could also be a "win-win" situation for your kid, too because the scouts are at the games and might see your kid play, but all of that depends on the playing time your son gets and your son's abilities. Probably the drafted kid will play on those scouting days,and if your son does get playing time, it needs to be good. And then, of course, there is the possibility that the coach will decide to play the "D & F" no matter what, leaving your son sitting the bench, being seen by no one.
Secondly, I can speak about California JUCOs because my son attended one of the top programs in the Orange Empire two years ago. First of all, if your son wants to play for a CA JUCO and he does not reside in CA, it is HIS responsibility to write a letter or pick up the phone to that CA JUCO coach to make the initial contact. CA JUCOs cannot initiate any contact with players from other states---it is against their rules. Once an out-of-state player makes first contact, then the CA coach and the player can talk to each other all they want. (So for those of you waiting for the CA JUCOs to call, wondering why those calls don't come, you know now what to do!)
The next thing about CA JUCOs that you need to know is that that they cannot offer any scholarship monies to any player....also against their rules. So, if your son is from out-of-state, plan on paying out-of-state tuition. Many do not have dorms, either, so plan on paying CA prices for an apartment. We payed about $15,000 to send our son there, all expenses included, and that was even with two other roommates sharing his apartment.
Competitively, CA JUCOs are really tough, and could beat most D-I programs on the field. They play 50-70 games/year in "baseball weather" all year round. They even have a full agenda of fall games--usually about 15-20, if you include "unofficial scrimmages". BUT (and this is really important), before you send your son to a CA JUCO, go back and read what I said about the "Draft and Follow" issue---since these JUCOs do not have to invest any monies to get a player, there are no commitments to any player. As my son's Orange Empire coach told us, "everybody rolls the dice, hopefully for a nine month honeymoon." The fall season is nothing more than a long tryout for the starting spots!! And those "draft and follows" will certainly figure into the mix heavily, and the MLB will pressure those coaches to see the "D & Fs" play since they are the only ones with money on the line.
Now on to more general observations about JUCOs in general. Competitively, most are really good, and most play a lot of games,so your son will get plenty of baseball. NJACC schools, (and the NWAACC schools here in the Pacific Northwest) can offer athletic scholarships. "Draft & F's" still figure into the mix, but so does the scholarship kid, when it comes to getting a serious look and playing time.
Academically, JUCOs are probably not as challenging as a 4-yr-school, but that is by design. Many students who attend JUCOs are trying to find an economical way to get the core academic requirements finished, so most of the classes are "the basics". If your son went in with good grades, he usually can keep up with the classes well. If your son did not have good grades from high school, he has the chance to pull his GPA up to 4-yr standards. But again, a warning....both of my son's roommates took remedial and easy classes rather than anything challenging, just so they could be eligible to play baseball. When they tried to transfer those courses to a 4-yr school (or even another JUCO), they didn't count. Be sure your son is taking meaningful classes towards a degree. Now with the 40/60/80 rule for JUCO transfer in effect, only meaningful classes will make your son eligible to play baseball after he transfers to an NCAA 4-year school.
Finally, I want to address the dorm issue at a JUCO. While a few schools do have dorms, most do not. If I had it to do over again, I would have tried to find a JUCO with dorms. Since JUCO teams play so many games, and a kid has to keep up with academics (in meaningful classes), it is a lot for a kid who is new to the college scene to clean an apartment, cook, grocery shop, do laundry of his regular clothing AND uniforms for all those games, weight train, attend practices, drive to and from school and games, and adjust to roommates, and STILL have anything left to play his season. Most of the baseball players my son knew (at both JUCOs) who had apartments lived in absolute filth simply because they didn't have time to tend to its upkeep. Baseball and school needed all the attention, and even then, one or the other was somewhat compromised. (A few of those kids flunked out, or failed on the field to end their baseball careers.) His own apartment in CA should have been torched rather than cleaned upon move-out, and those guys all tried hard in there up until January when season prep began...then it all fell apart. (Did I mention that his roommates were also baseball players?)
This last year, we could not afford to send our son back to the CA JUCO, so he lived at home and went to a local JUCO. He was a starter, so he played all those games. Although we made him do most of his own upkeep here at home, he expressed deep appreciation for not having to do all the cooking, or buy food, and we helped wash his uniforms during the season and finals week. All in all, he played better, had better grades, and didn't feel under constant pressure and stress. He actually enjoyed life again. He has also seen his sister's experiences at her 4-yr university, both in the dorms and in apartments over recent years..(she is a SR and will graduate in Dec of this year.) She, too, did better with her academics and juggling campus life in the dorms vs. the apartments, and she is not an athlete...only a science major. In conclusion, by taking all he knows into account, my son now proclaims, without any hesitation, that from now on he will be "a DORM GUY with a FOOD PLAN"-to quote him.
Sorry to be so lengthy, but I hope what I've said will help someone who wants to go the JUCO route.