The biggest benefit at JUCO is the essentially unlimited practice time and the full Fall schedule. While there is a limit to the number of Fall games, many of these are 14-16 inning games. There is a lot of playing time to go around in the Fall season. It's like a full time baseball camp with some school mixed in.
The talent at the top end is pretty high. Wabash beat Purdue this weekend and struck out 15 in the 9 inning portion. It's hard for people to believe this but Wabash probably has better arms than any team in the Big 10. Cowley took down Wichita St 18-11. Iowa Western jumped all over Iowa's ace who is a projected high draft pick. It was 11-2 before Iowa's depth took over in the later innings.
I'm of the opinion that only the top 1% are capable of playing out of high school in the SEC/Big 12/ACC. JUCO provides a home for all of the kids that chose Arkansas/Mississippi St/FSU etc out of high school when they should have picked La Tech/Southern Miss/South Alabama etc.