DVDs are manufactured a bit differently than CDs and can withstand more abuse, at least on the label side. On a CD the reflective layer is protected on the top only by a thin epoxy coating over which is the silk screened label. It's *very* easy to scratch the top and ruin the reflective layer (both pressed *and* burnt) of a CD. DVDs have the reflective layers sandwiched between layers of polycarbonate. The label side of a SS disc is tough (it's as thick as the bottom) and can be scratched without affecting the playback layer (bottom). Writing on, putting labels on, even using mild solvents on the label side of a DVD will not damage the playback layer as you have to get through that polycarbonate layer first.
Here's how DVDs are constructed (this mentions recordable specifically but pressed are not much different - mainly lacking the dye layer):
A single-sided (SS) disc is composed of a recording side and a dummy side while a double-sided (DS) disc consists of two recording sides. The recording side of a DVD-R and DVD+R disc is a sandwich of a number of layers. First comes a polycarbonate plastic substrate, then an organic dye recording layer followed by a metal reflective layer. The dummy side of a single-sided disc consists of an additional flat polycarbonate plastic substrate (sometimes with an additional metal layer to obscure the bonding layer from view for aesthetic purposes). An adhesive then bonds the two sides together for the final disc. Some single-sided discs are also topped on the dummy side with additional layers that provide surfaces suitable for labeling by inkjet, thermal transfer or re-transfer printers.
So... you want to be more careful with the *playback* side of a DVD as scratches can affect playback, although they *can* be buffed out if not too deep. You can ruin a CD (or CD-R/RW) by scratching the label side but a scratch on the playback side can be buffed out.
Here's how DVDs are constructed (this mentions recordable specifically but pressed are not much different - mainly lacking the dye layer):
A single-sided (SS) disc is composed of a recording side and a dummy side while a double-sided (DS) disc consists of two recording sides. The recording side of a DVD-R and DVD+R disc is a sandwich of a number of layers. First comes a polycarbonate plastic substrate, then an organic dye recording layer followed by a metal reflective layer. The dummy side of a single-sided disc consists of an additional flat polycarbonate plastic substrate (sometimes with an additional metal layer to obscure the bonding layer from view for aesthetic purposes). An adhesive then bonds the two sides together for the final disc. Some single-sided discs are also topped on the dummy side with additional layers that provide surfaces suitable for labeling by inkjet, thermal transfer or re-transfer printers.
So... you want to be more careful with the *playback* side of a DVD as scratches can affect playback, although they *can* be buffed out if not too deep. You can ruin a CD (or CD-R/RW) by scratching the label side but a scratch on the playback side can be buffed out.