There are 2 main reasons for using "image catalog"
1. You can load the CD's during working hours, and run the update off hours. Running the update should be faster from the catalog, and bypasses the "Install next CD" message that requires the operator to reload the CD drive several times. This may reduce the amount of time the system is offline.
2. If you need to load to multiple systems, the image catalog might be easier to send to the remote system than the CD's
There are three main advantages of using CD drives over image catalogs that I can think of:<ol>
<li>You can process CDs with a CD drive if you don't have an image catalog, but you can't process CDs with an image catalog if you don't have a CD drive.</li><li>CD drives don't require disk space to store the CD images.</li><li>Proper functioning of image catalogs often requires PTFs beyond the base set.</li>
You have to decide if any of those advantages have any actual value.
Pretty much everything else favors image catalogs -- speed of operation, flexibility, manual intervention (lack of), program control (unattended operation). With image catalogs, you don't even need CDs, just use CD images. Images can be transferred from PCs to the IFS, potentially over the internet.