For example, if you have a testing section on a CD, you could store the questions and answers on the web so that you can update and change the question bank as often as you like. Of course, this assumes that your learners have access to both a CD-ROM drive and the Internet. More than you'll ever need unless you want to put an hour's worth of video on it. CDs are good for decent quality video and sound. Unless you have your own server, you're usually limited to 5-10 MBs.
Compression is a way of life.
Because download time is such a limitation for the web, media elements are almost always compressed. Media elements can't match the richness, quality, and speed of their CD-ROM counterparts. The computer may have an occasional crash, but in general, if you can get the CD into the hands of your users, they'll be able to run it. Your program is going to look and act as planned. Depends on which way the wind blows.