bball - great question - Speaking from experience, RightyShortstop played 3 sports in HS. Baseball, Basketball, and Golf - He was captain of all three teams and earned 10 Varsity letters (4 golf - boys golf is a fall sport here, 3 baseball, 3 basketball). He is only playing baseball only college. In the recruiting process, college coaches liked to talk a good game about how great it was to be a 3 sport athlete, but in reality, we found that they just recruit baseball ability. Admissions counselors LOVED the three sport thing.
Most of all, coaches and ad-coms liked the captainships. My son has always theorized that playing all three sports held back his baseball development. He has improved quickly in college ball by concentrating on baseball. He thinks that some coaches recruited him because they also believed that playing all three sports had held back his baseball development, and thus saw "upside" for him as a college baseball player.
Prior to Junior year we went on an unofficial visit to a mid D1 school where we had a long talk with the coach and asked him his opinion of playing three sports. The coach gave the usually mumbo-jumbo about how he recruits athletes and then qualified it by talking about baseball ability. Finally, he gave some good advice that my son followed. He said "If you are going to be captain, play all three. If you can't play the sport AFTER HS make sure you play it IN HS. If you stick with all three you will probably never know if playing them all helped or hurt your baseball career. However you will always be sure you had great HS memories."