What is the collection which you are trying to back up? Is it a video collection? Is that why you were asking which media to use, so that you could play the video through a DVD-player linked to a television? If that is what you were asking, it would depend on the DVD-player you wanted to use the back up disks with. As your computer can obviously record to either medium, it must be able to play either DVD+/-RW disks.
If it is the DVD player issue which is the problem, you could look to see if your player is listed on this site and find out which medium you would need to use.