If you would actually consider, there are only slight differences between the two. The only difference is that layering is usually more subtle. This means that you can barely see the ends of the cut because they will all be layered against each other that they will seem to cascade. The step cut is known to be a little bit more obvious.
The cuts are going to be blunt so that you will know where each layer of the hair ends. People can choose whichever they think will be more perfect for their needs or the type of hair that they want to have. If you want to understand further, a layer cut is similar to a feather cut while the step cut shows the heavy chops more.