If it is WORM, quality matters most. I agree (lowest speed settings).
For mass distributions, one could maybe sacrifice quality a bit (eg. 8× or 12× DVD burning).
If it is a re-writeable disc, it dependsbon the purpose.
If I use a CD-RW to test as audio CD on an old CD player, I should not just burn at low speeds, but also use a full-soze desktop disc drive. They achieve higher qualities at the same speeds (at low speeds: no difference) than slim laptop disc drives, but require 12V instead of 5 volts.
If I use it inside computer drives with good error correction, and will rewrite the disc anyway, then quality is lesser important.