It also depends a lot on what kind of player you have, what kind of burner you have, and what firmware your burner has, as well as the brand of media.
I mostly use DVD+R media these days because the burners I have are faster at +R than -R. I used to use/swear by only -R media, but these days it doesn’t matter much.
My main player is a Pioneer and will play pretty much everything, except the crappiest media. My second player is a Tobishi and it will play almost any single layer media but has trouble playing dual layer recordables. Finally I have an old Samsung player from 1998 that’ll only play the highest quality media. I mainly keep it around because if something plays on it, it’ll pretty much play on anything.
My main burner now is a BenQ 16X DW1640. I also have an older Lite-On 8X drive installed in my desktop but I don’t use it much.
Here’s my current experience with recordable DVD media:
Dual Layer +R:
Excellent results with Verbatim/Mitsubishi DVD+RDL. This is sold as 2.4X speed but it’ll burn at up to 8X speed if your burner supports that speed. My BenQ drive will burn it at 8X without problem.
Mediocre to OK results with media with a RICOHJPN manufacturer code, but only supports 2.4X. (Imation and Melody branded disks.)
Bad to Poor results with RITEK manufacturer code, only 2.4X. (Ridata branded disks.)
Single Layer +R 16X:
Good results with Ricoh branded disks and Imation “Rainbow” branded disks.
Mediocre results with Imation “SO-HOT” branded disks.
Poor to OK results with Melody branded disks.
Single Layer +R 8X:
Excellent results with Maxell disks.
Usually excellent results with Ritek or Ridata branded disks, though I’ve had a few problems recently with some spindles with high failure rates.
Good results with Philips and BenQ disks.
Poor to mediocre results with Sony, Iomega, Melody and Zio branded disks.
I would recommend not buying 16X until quality is improved and pricing comes down (the reliable brands are still expensive). For 8X I would recommend Maxell for important things, BenQ for reliable lower-priced disks. For DL I would only recommend Verbatim/Mitsubishi currently.
Even so, I’d recommend buying a couple of different 10-pack spindles of different brands to see what works well with your combination of hardware. You’ll note that I have had good results with BenQ while someone else here had problems with it.