Dvd/CD Drive won't read Blank DvD-r/DvD-RW

  A-

DVD-R:
Benefits: Better DVD playback compatiblity within home DVD players.
Drawbacks: Older technology and less money behind the format means that they come out with faster media and burner technology slower. You will frequently see DVD burners that will support (for instance) 16X DVD+R and only 8X DVD-R.
DVD+R:
Benefits: Faster speeds, more inovations like Double Layer discs (8.5 GB)
Drawbacks: Will not play is some home DVD players. If you know your home DVD player will play DVD+Rs then there is no reason to not use them.

  B+

Commercial Answer
The truth is that the two competing technologies use different formats. No single company "owns" DVD and both technologies have their "champions".
DVD-R/RW was developed by Pioneer. Based on CD-RW technology, it uses a similar pitch of the helix, mark length of the 'burn' for data, and rotation control. DVD-R/RW is supported by the DVD Forum, an industry-wide group of hardware and software developers, and computer peripheral manufacturers. The DVD-R format has been standardized in ECMA-279 by the Forum, but this is a private standard, not an 'industry' ISO standard like the CD-R/RW Red Book or Orange Book standard.

DVD+R/RW is also based on CD-RW technology. DVD+R/RW is supported by Sony, Philips, HP, Dell, Ricoh, Yamaha, and others, and has recently been endorsed by Microsoft. DVD+R/RW is not supported by the DVD Forum, but the Forum has no power to set industry standards, so it becomes a market-driven issue.

Technical Answer

DVD+R is a dvd disc that allows multiple layers for one disc where as dvd-r only allows one layer. They will not compete to become the de Facto standard, because they are both here to stay. Multi layer DVD+R can allow extra capacity per disc than DVD-R hence its high cost!