Agreed....
Cost and Quality (as well as turnaround time) Pretty much will determine the method of printing you should use.
As quality increases cost usually follows. You should determine what your budget is and then find the best quality printing method you can get for that price.
If you figure this out in the begining, you will know how to design your piece. B/W, Spot color, Process color, etc..
Digital printing usually refers to what amounts to high quality color copies. Although as mentioned above some of the newer machines such as the Indigo line of offset digital printers are pretty remarkable.