Shoulder raises isolate the deltoids. They are an important stabilizing muscle in a multitude of different exercises, ensuring proper form and control during a movement.
Activating the deltoids involves shoulder rotation. The movement can be done with dumbbells or a cable.
The variations in shoulder raises change the direction of the motion, putting more emphasis on a certain part of the deltoid.
Instead of bringing the weight out front, bring the weight to your side.
Using a cable provides a constant resistance, making the variation more strenuous throughout. That said, there is no overwhelming difference in results. The movement is the same.