They are actually very simillar.

DVD-R:
A write-once format that is compatible with many existing DVD Players, Recorders and DVD-ROM drives. Can only be used in DVD Recorders and Burners that support DVD-R recording or multi-format recording (drives that record "plus" or "dash"). Holds 4.7GB of data or video. Typically, it can hold 2 hours of MPEG-2 video on standard (SP) speed setting.

DVD+R
Another write-once recordable DVD format developed seperate from DVD-R. These discs are basically the same as DVD-R discs. They hold 4.7GB of data or video and are compatible with most DVD Players and DVD-ROM drives. They can only be used in DVD Recorders and Burners that support DVD+R or multi-format recorders.

to see other types of dvd formats you might be intrested in:
http://dvr.about.com/od/dvdrecordableformats/f/faq4.htm

DvD-R: Write once, better for Video as widely accepted by home DvD players.

DvD+R: Write once BUT data can be added later (not RW, but still accessible). Better for data as most Computer DvD players can read it and you can fill half the disk, then add a quarter, and the complete it a year later (as an example).

Hope that helped.

I did some searching and DVD+R seem to be better for data and DVD Video Burning, and also last longer in years so they are better for your photo and Camcorder back up etc. Here is a Web Page to look at. Towards the botom of the web page the Author explains about DVD+R Being Better.
www.adterrasperaspera.com/blog /2006/10/30/how-to-choose-cddv d-archival-media

DVD-R - pronounced ‘DVD R” (not “DVD dash R”)

DVD-R was created by the DVD Forum (see it at http://www.dvdforum.org/forum.shtml ). The most common DVD-R is a write­once 4.7gb “general purpose” disc, which is roughly equal to 120-minutes of standard playing lime.

Once recorded, a DVD-R can be played on most home DVD players. (Advertised as compatible with 90%+ of home DVD players.) General purpose DVD-R media is currently the cheapest & most common, and the newest DVD-R drives write at up to 4x. “General-purpose” discs are part of the industry’s copy-protection scheme, which employ CES scrambling to protect movies and music and game discs from being copied. These discs can be burned by “general-purpose” DVD writers such as the Pioneer DVR-A05/A04/103, Panasonic LF-D3 1 1/D321, Toshiba TSDR5002, Apple Superdrive, etc. Such drives cannot copy the playback descrambling codes on DVD movies or game discs, preventing easy duplication of commercial discs.

DVD-RW - pronounced ‘DVD R W” (not “DVD dash R W”)

DVD-RW was created by the DVD Forum (see it at http://www.dvdforum.org/forum.shtml ). Generally comes in the single-sided, single layer 4.7gb capacity, which is roughly equal to 120-minutes of standard playing time.

In contrast to the write-once DVD-R types, the DVD-RW is fully re-writable or erasable up to 1,000 times. However, unlike the older DVD-RAM format, these particular erasables are NOT “random access”, meaning that you cannot erase bits and pieces of them. Instead, you have to completely erase the whole disc to reuse it The DVD-RW can be played on many home DVD players, but not as many as the DVD-Rs.

DVD+RW - pronounced ‘DVD plus R W”

This disc type was created by the “DVD+RW Alliance”. A few companies who back the DVD Forum (above) are also active in the DVD+RW Alliance, but the two standards are not compatible.

The first “plus type” DVD recording format is DVD+RW. It, like DVD-RW, is a rewriteable 4.7gb DVD disc. DVD+RW, does have a couple of technical advantages — (1) lossless linking (which enables some editing after recording without a full erasure that DVD-RW requires), (2) a special drag-and-drop file support on the desktop (otherwise known as DVD+MRW). Unfortunately, the DVD+RW disc type does not compare well with DVD-R as far as DVD playback compatibility. However, the actual level of DVD workability on players of DVD+RW is claimed to be about equal to DVD-RW.

DVD+R - pronounced ‘DVD plus R”

This disc type was created by the “DVD+RW Alliance”. A few companies who back the DVD Forum (above) are also active in the DVD+RW Alliance, but the two standards are not compatible.

The newest “plus type” format is DVD+R. It’s write-once disc is aimed at becoming more compatible with home DVD players. However, the fact is that so far it is only about as compatible as DVD-R discs are. Also, DVD+R discs are more expensive in today’s market, and are not burnable by 1st generation “plus-type” burners, which were designed only for the DVD+RW rewriteable discs. Like DVD-R “general purpose” media, DVD+R cannot copy the descrambling codes found on DVD video discs, so commercial discs cannot easily be duplicated. DVD+R drives have recently reached the same maximum recording speeds as DVD-R drives. (4x)
(once you write some data to +R disc, you can also add some more data later,again and again. but you can not erase the data once you writen.)

DVD-RAM

DVD-RAM is used for data backups and storage, and for editing of video or audio content prior to the production of a final distribution DVD. The DVD-RAM disc type is made to act a lot like a hard drive, where the disc can be formatted for Macintosh or Windows type computers. It can handle 100,000 or more erasures, and should last for many years. Of course it is not playable on most DVD players. Type 2.0 DVD-RAM discs can be removed from their cases to enable playback on the few players in which they are compatible. The newer DVD-RAM drives can handle any sized such disc, including 2.6, 5.2, 4.7 or 9.4gb discs.

Some drives support two or more of the above DVD formats. Most add support for CD-R / CD-R W burning as well. But, no currently-available drive has support for all of the D VD / CD formats.

Well I came here to find the answer as well. I started backing up movies about two years ago, and was always using +R. I have a pioneer up-converting DVD player which supports both -R and +R formats. The problem I am running into is, while watching a movie burned on the +R format, it often freezes, skips, and sometimes can't continue to read the disk, a problem that is intermittent. If I make it all the way through a movie burned on +R without this happening, I feel lucky.

Oddly, I can sometimes watch a +R disk with no problems, while at other times the same disk freeze and skip. Also, if I loan a disk to a friend or family member, if it was burned on +R, they often cannot watch it, or have the same problem with it freezing. I never have any of these problem with the ones burned on -R. I realize, a lot of people still have older DVD players that do not support the +R format, but mine does, and I still have problems with it.

Granted, I am backing up movies and not other types of data, and as previously mentioned, -R seems to be better for movies, and +R for data.

I have been finding that I am better off going back through and re-burning stuff from the +R disks to the -R. If I am watching a +R, and it starts to skip. I simply pop it into my computer and burn it right from the +R disk on to a -R, problem solved. I am a little ticked that I have wasted so much time and money on the +R format, but what can you do.

Nobody cares about the different forums and alliances and all those useless facts about dates and development.

DVD-R is supposed to be slightly better for movies.

DVD+R is supposed to be slightly better for data.

I have been told that these slight advantages have something to do with the way the drive organizes the information on the disc in either format. In simplicity, DVD-R writes in sort of a continuous fashion better for reading video, while DVD+R sort of scatters the information around on the disc in a way that is better for the drive to process data.

I can't honestly back this up because I don't know if it is correct, but this answer makes the most sense if it is true. Hopefully a computer genius can edit this answer if it is wrong, but maintain the basic idea of my response--to actually define a difference in the two formats for a consumer who is buying single-layered, blank media to use with a DVD burner that will write on either type. I think that's what we want to know!

lets put it simple. a +R will not work in ALL older dvd recorder nor older dvd players. -r will work on all players and all recorders. :) unless ur positive u that ur computers burner supports +R leave it alone. get a pack of -r. as for tech answer. there is none they both write data in a very simliar form. the difference is too small to notice. this is just a older bluray and hddvd problem but the + and - R problem has now been solved with modern day players and recorders. cheers. (^.^)

i have read quite a few of ur amswers, im nt a comp wiz but i do belive that DVD+R's are better for storing data, i.e. backing up your photo's, and that DVD-R's are better for burning movies, i had used a dvd+r to record a film and played it in my dvd player and some times its ok but other times it will skip and jump back in chapters and so on, burned the same film to a DVD-R and playback was fine. all i buy now is DVD-R's as you can do everything without a problem so i would recomed to just use DVD-R's.
one other thing is that i found with the DVD+R i could erase and re-write on the disc even tho its not an RW ?:S?

Also I remember there was a differance in the way the data was written to the disk. -R is one continious stream and +R is broken into sectors and tracks.
I may be mistaken I have not thought about that for years.

DVD+Recordable defines a standard for recordable DVD drives and media defined by the DVDRW Alliance. Often called "plus R", the format is write once (compared to DVD+RW which can be erased and rewritten). The single sided discs can hold 4,700,000,000 bytes (4.38 Gigabytes at 1024 bytes to the kilobyte) with double sided discs holding twice as much. There are no dual layer single sided recordable discs. This format competes with the DVD Forum DVD-R specification. DVDR help DVDR information.

DVD-Recordable defines a standard for recordable DVD drives and media defined by the DVD Forum. Often called "minus R", the format is write once (compared to DVD-RW wich can be erased and rewritten). The single sided discs can hold 4,700,000,000 bytes (4.38 Gigabytes at 1024 bytes to the kilobyte) with double sided discs holding twice as much. There are no dual layer single sided recordable discs. This format competes with the DVD+R format.