We install cobblestone edging too. It is quite popular in the area we live in. The photos below illustrate some of the steps we go through during the installation process. Generally speaking it is more expensive than the concrete edging. The cobblestones themselves are the main factor for the additional expense. They really look nice and the end product reaches the same objective as the concrete edging does. The cobblestone outlines your driveway nice, giving the driveway crisper lines. It will keep the mulch from migrating from the adjacent bed also. The edging also helps to direct rain water. For instance in this job the rain water will go down the driveway to the street in lieu of going into the bed next to it. Whether you decide to put in cobblestone or concrete I hope you give us a call, we would love to do it for you.