A far as my experience goes, absolutely nothing. I know on CD-RW you can delete EVERYTHING and start over from scratch...not sure if you can do that on CD-R. That may be the difference.
This is what the difference is. CD-R's are more commonly found in stores everywhere, but when you place information, mpIII's(how leet was that?) or whatever it is you are planning to use on them, it closes the disc and makes it impossible to delete anything on it. At least, in my experience. Which is why they're called CD-R's, (CD-writables)
CD-RW's you can erase it all and start over, meaning you can use the same disc twice, three times, whatever. This is why they're called CD-RW's(CD-rewritables).
I think it has something to do with compatibility as well. Is there a CD-R+ drive? And I'm sure I've seen some DVD-R's labeled, DVD+R. Eh. Perhaps the + has a compatibility with the + drive and a backwards compability with the other drive as well... because I'm sure that the + must cost more...
I've seen CD+R and CD-R+, I think. The CD-R- was an assumption, though it's possible that the CD-R+ is a brand, because I haven't seen the big names like Philips do them. I'm not curious enough to do a search though, and in any case, searches don't include "+" in them.
There are no CD+RW standards (that I know of). The CDR(W) standard has been worked out a long time ago. Currently, only the dual format DVD standards are the tricky ones. Each standard is basically the same, but they don't work with each other. Most burners are dual format now anyways.
2014 is going to be a good year. More content, more streamlining. Be a part of history!