I got a subdivided mesh/face where a road should run along. So we have an outer and an inner edge. What I want to do now is delete all these faces that lie within the outer and inner cut/edge. Of course you can do that with circle select but I wonder if there is a faster and more efficient way?
If you have a cut in there, you should have separate Mesh Islands.
Hovering your mouse over the island of choice and pressing L will select the Linked Faces. You can look in the Operator Panel for additional options that will limit the selection, like Seams, for instance.
Alternatively, select just one element and hit Ctrl + L to select the linked faces, regardless of where your mouse is at that moment.