Honestly there aren't one or two discernable differences that will make the choice absolute. The only one thing that would matter is if you have an older DVD device that only supports the "-" format (or simply a device that only supports one or the other). Other than that you're good with either. I generally use the "+" format for better error handling.
For archiving data/music/games I'd use +
This is the link innocentdevil posted (was just missing a little at the end) -
http://en.wikipedia.org/wiki/DVD%2BR
An excerpt from that web page:
The DVD+R format is divergent from the DVD-R format. Hybrid drives that can handle both, often labeled “DVD±RW”, are very popular since there is not a single standard for recordable DVDs. There are a number of significant technical differences between the “dash” and the “plus” format, although most users would not notice the difference. One example is that the DVD+R style Address In Pregroove (ADIP) system of tracking and speed control is less susceptible to interference and error, which makes the ADIP system more accurate at higher speeds than the Land Pre Pit (LPP) system used by DVD-R. In addition, DVD+R(W) has a more robust error management system than DVD-R(W), allowing for more accurate burning to media, independent of the quality of the media.
