One of the major drawbacks to using recordable media is that they are prone to scratching. A scratched disc cannot be played in the computer, it will simply give an error every time you try to copy data off of it. This is a potential disaster if the user has erased their system.
Transferring data using a flash drive gives you certain advantages. The drives themselves are incredibly small, a little bit larger than your keys. So flash drives can be transported many ways: you can slip one easily into your pocket, on your key chain, or around your neck using a lanyard (which a lot of drives come with). Some companies have even integrated flash drives into common devices such as watches, pens and Swiss Army knifes. Besides being small, flash drives come in a wide assortment of capacities. Drives get as small as 16MB and at the time of this review have peaked at 8GB.