While some will argue DVD+R is best for storage and DVD-R is best for movies, the actually differences are negligible. Both are just as adequate for either task, and will last the same length of time. How long that time is, though, depends on the media itself. Unlike bought DVDs, recordable media doesn't last a lifetime and depends greatly on the storage conditions (temperature, humidity, use of labels, etc) as well as the original quality itself. Some will fail out of the box while others will last 20+ years.
The best advice is to purchase reputable brands, store in a clean, cool, dry, dark climate, and don't use sticky labels or write on them. (The ink/dye/glue can actually eat through the DVD's thin metallic layer over time.) Pull them out every few months and randomly try opening files, and burn a new set of DVDs every once in a while. Keeping two sets of DVDs isn't a bad idea if it's truly irreplaceable data.
As to the problems you encountered, it could have been a bad batch of DVDs or it could be the drive...when a multiformat drive goes bad it may have problems reading/writing a particular format.
Hope this helps,
P.S. Keep in mind that not all DVD drives and DVD players can handle both formats, so if you're going to share files or home videos check what the other person's drive can handle first.
I have just purchased a dvd burner for my computer for burning some home video and backing up files such as personal records, photos and other personal files. I am trying to figure out which media to use and I now have a headache. I bought 1 pkg of DVD-R and 1 of DVD+R to test and see how they would work on my DVD player. I burned some home video and the +R did not work well at all. It skipped and jumped and was basically unwatchable. I then tried the -R and it worked perfect. (I burned more than one of each disk to make sure that it wasn't just a bad disk and the results were the same.) I also backed up my photos on -R media. I decided to research and see if I could find some info on what was recommended and see if it matched my experience and I read that -R media is not recommended for backing things up because of some kind of flaw in the disc design and also that the discs are not good to store files long term. So now finally I am to my question. Which one is best for backing up important files and things and how long will the discs last? I keep all copies of these files also on my computer hard drive and I usually back up once or twice a month depending on how many changes I make. Are these disc only good for months or years or how long? I don't mind backing up the exact same things several times a year to make sure I am not going to lose it but is that necessary? Basically I just need some guidelines about using this as backup. Thanks in advance for your help!
(My computer is a Dell running Windows XP Home edition and the drive is a Lite on 20X DVD writer and I am using Ashampoo to burn the files. Tried Nero and Roxio too and didn't like either of them. If I need to list anything else let me know!)