there different formats kinda like beta vs vhs all newer standalone dvd players support both formats some older model dvd players may have trouble playing the DVD+R but if you booktype them to DVD-ROM you should be fine or use the DVD dash R format. read this vvvvvvv http://www.cdfreaks.com/reviews/Why-DVDRW-is-superior-to-DVD-RW http://www.k-probe.com/bitsetting-booktype-faq.php http://forum.digital-digest.com/showthread.php?s=&threadid=46559
Usually none unless a person has a very old player. The big reason for "dash" and "plus" is because the "plus" alliance didn't want to pay royalties to the older DVD Alliance, "dash". As mentioned, almost all new players support -R and +R with many supporting more formats. +R and +R DL booktype to DVD ROM for broadest compatibility, DVD ROM being the universal player format. I booktype, but it's more habit than necessary. In the years of DVD backups, I've seen one cheap (promo) player that played only DVD ROM. At the time I didn't know if it would play -R because I didn't have one to check with. Here's a link to a short read on the DVD +RW Alliance with mention of the rival DVD Alliance. http://en.wikipedia.org/wiki/DVD+RW_Alliance
