Before the MLB Draft league was included the New England League (NECBL) regularly ranked second behind the Cape Cod League and just ahead of the Northwoods league. The league has several MLB draftees each year and plays really quality baseball. Due to its proximity to the Cape some players get "a taste" of the Cape at the end of the year if their team doesn't make the playoffs.
Every league tends to be willing to sign pitchers; many of the better pitchers are on strict pitch or start counts. Position players are more apt to stay and its harder to latch onto a team later on. It may not matter where you play (if higher tier league) but THAT YOU PLAY. Some leagues also allow position players to play multiple positions (don't limit you), which can prepare you for your college season the following year.