not much difference actually - CD and book, you can and should do it on the computer as your time permits, and you should do as many questions on computer as you can to get used to the eye strain, exam itself is a killer long day, nine hours, and towards the end you may get eye strain, so practicing material on the computer as much as possible is the best, the other big thing is the pictures on the cd, they are really good quality, and helped me retain some key facts, although as I recall there were not too many pictures, but the pics were of very high quality. I might get MKSAP 13 for residency, hopefully it is equally good or even better. Pretty sure that they are the exact same questions and explanations on the CD and book, only you can get graded and guage your knowledge on the cd, my scores ranged anywhere from 42% to 78%, cumulative approximately 65%, but the knowledge that I attained from that cd was the best thing about it, you feel more confident, and you can easily do a variety of questions afterwards, I wish that they had this text and cd for each and every subject, but it does an excellent job for Medicine,
good luck.