The behind the neck press puts more emphasis on the meidal deltoid than front presses. I like using a smith machine with this exercise to gain more control.

I also like seated cables presses because it allows me to keep the elbows back without pushing my neck in a forward position.

I also agree oen should not come down too far and that many people turn shoulder presses into an upper chest movement by arching their lower backs in order to lift more weight.