The one thing that I will say, is that its really all about genetics. Rep range doesn't matter.
Shoulders are my best bodypart. No matter what I do for them, high rep, low reps, moderate reps, they grow.
Chest is my weak area, and no matter what I do for them, high rep, low reps, moderate reps, they are extremely stubborn to grow.
Really, I don't think rep range really matters if the genetic potential is there to grow, the bodypart will grow. The same with machines vs free weights--does not matter.