Indeed, the brand name means very little. What is important is the Media ID code, which reveals who really manufactures the discs. (For example, discs branded TDK may actually be manufacturered by Ritek, Hitachi/Maxell, etc.)

People say not to buy Memorex discs because they're crap quality. I had one box of discs with a CMC media ID code which were awful - but the next batch may be made by Ricoh and perform much better.

Check out these links:
Blank media quality guide: http://www.digitalfaq.com/media/dvdmedia.htm
Videohelp media list: http://www.videohelp.com/dvdmedia
CD Freaks blank media forum: http://club.cdfreaks.com/f33/

For UK disc buyers: SVP is an online store that actually tells you the Media ID of the discs you are buying. I've found THESE DL discs to be very good value.