CD-RW - 11 Mbps transfer rate, 0.5 Gigabytes total storage, $2.50 per disk
DVD-RW - 11 Mbps transfer rate, 4.5 Gigabytes total storage, $2.50 per disk
Compact Flash - 150 Mbps transfer rate, 2.2 Gigabytes total storage, $250 per cartridge
Hard Drive - 150 Mbps transfer rate, 250 Gigabytes total storage, $250 per module

Practical Conclusions:
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Compact Flash is best for portable electronics. They have durability, low energy consumption, access speed equal to a hard drive, and storage capacity adequate for just about anything. They can be swapped out and/or upgraded without throwing away the portable device itself.

Hard drive is best for desktop computers. Dozens of CD's and DVD's can be replaced by a single (external) hard drive for roughly the same price. And hard drives are faster anyways. In my opinion, the external dimensions of hard drives, CDs and DVDs, should be designed so that they will fit inside a small bank safety deposit box, often the preferred method of businesses for safekeeping of proprietary data.

CDs or DVDs must still be used for retailing individual software packages. They are also convenient for making backup copies of utility software, or shareware, which tend to require small amounts of storage; and for backing up data from a single project one might be working on currently.