As you can see, there are a variety of situations in which a step drill bit can completely replace your reamers. However, when looking at the big picture this isn't the case. There are still plenty of scenarios in which using a reamer will be more effective. Most notably, when the hole that you are creating is going to be fairly deep or the material that you are working with is too thick. The final conclusion is that it is ideal to have both in your toolbox.