My 1 year old Pioneer set top player won't even recognise +R media, which kinda sucks. So just like Moth3r, for me it all comes down to what is most compatible with the gear I have. I stick with -R as it seems more compatible with more brands of gear.
This article talks about using archival quality DVD media and explains why +R is better:
http://adterrasperaspera.com/blog/2006/10/30/how-to-choose-cddvd-archival-media
The most important thing I've learned so far is to get decent media that will last. I've bought heaps of discs that are fine to begin with but after 6 months or so they crap out when the die fades and refuse to play properly or even copy on a PC anymore.
This article covers the major DVD manufacturers and ranks the quality of the blank media available. It also mentions which companies developed/support each format and has info on DVD-RAM at the bottom of the page:
http://www.digitalfaq.com/media/dvdmedia.htm
The general opinion on the net seems to be that Taiyo Yuden media is the best, but anything from Japan is also very highly regarded (Note: for people in NZ, forget about any brand of Japanese media. Currently, all DVD media sold here is made in either China, Taiwan or worse).
If your player accepts +R and you want the absolute 'Rolls Royce' quality of DVD media, then go for Taiyo Yuden DVD+R if you can find it.
Hope this helps.