The important thing is how reliably the disc can be written and read today. That is the other side of light sensitivity, and it's a significant one. Phthalocyanine dye has a narrower range for writability with laser light - the coherent, tightly focused and precisely calibrated light used in CD recorders. This wider power margin may mean that cyanine media is suitable for a greater range of recording speeds and laser powers. It may also mean that cyanine media offers a higher likelihood of compatibility with more CD recorders.
Compact discs use pits of varying lengths to represent data.
The pits are the same width and depth, but their length and the spaces between them vary. In CD recordable, the pits are replaced by optical marks that, when read by a CD player or CD-ROM drive, appear similar to the pits in molded CDs. It will also contain more of them, which allows for greater disc capacity, but that's a topic for another time. Using laser light to create a microscopic mark of a certain length on dye polymer is not a linear process. Because materials tend to respond differently when they are heated for different lengths of times, a laser setting that produces a light pulse that creates a mark of a given length does not necessarily produce a mark twice as long when the light pulse is twice as long.