Flat price for unlimited use of CD-ROM digital stock images if used within the licensing agreement. You can build a library of images for future use. Digital stock does not retain as much quality as the original transparency. Higher quality images are available. More control over image usage reduces likelihood of competing use of an image.
Costs can be considerably higher and licensing is much more restrictive.
Transparencies must be returned after they are used. Enlargements are less expensive. Manipulation of the traditional image is limited. Digital imaging allows for more versatile image editing. Commercial quality inkjet prints are sharper and more detailed than traditional prints.