CD-R(W) from different companies are not the same. I've learned about this about a year or so ago. I've read several website regarding this.
Companies such as Memorex, Sony, etc. do not make their own CD-R(W). There are manufacturers that make CD-R(W)s for Memorex, Sony, etc. These brand name companies could switch manufacturers and the consumers do not even know it. I've read that CD-R(W)'s manufactured in Japan, and a few other countries are the best in quality. There is no way to know where the CD-R(W)s were manufactured just by looking at the package. You have to put the CD-R(W) in your drive and use a software that can tell you where the CD-R(W) was manufactured (see whether your drive came with this type of software.).
I've read that Memorex makes bad quality CD-R(W)s.
I've read that Ricoh, Sony, etc. makes good quality CD-R(W)s.
If you are doing data backup, I would suggest purchasing an external hard drive or two, or make external hard drives yourself using a hard drive enclosure.