The Britannica on paper is more convenient to use if you do not have access to a computer or if you prefer to read physical books. It is also more durable and can be passed down from generation to generation. However, the Britannica on paper is also more expensive and less portable than the Britannica on CD.
The Britannica on CD is more portable and can be accessed from anywhere you have a computer. It is also more affordable and easier to search than the Britannica on paper. However, the Britannica on CD requires a computer to access, and it can be more difficult to navigate than the Britannica on paper.
Overall, the Britannica on paper and CD are not close substitutes. The best format for you depends on your individual needs and preferences.