I think of the Progressive, Turret, and Single stage like this
Faster, Quicker, and easier to make a mistake while learning. Typically takes some experiance to be competent at this level. Progressive presses do a function at all the stages everytime you pull the lever
Turret= Junior Varsity:
Not slow, not fast, and less complicated. Can still follow the steps fairly easy and if you have a good understanding problems are easily identifiable. Turrets bring a station the the round everytime you pull the lever
Single Stage= Pee Wee:
Slow, Very accurate, and the perfect place to learn all the basics and to build a good foundation. Single stage you have to bring everything to the bullet. Unless you change something it will do the same thing everytime you pull the lever.