I`m not an expert but
I`m writing this because lots of plus users have the same problems I had.
Several +R disc wasted, +RW not playable in standalone.
These drives are mostly Ricoh inside so the following apply.

http://www.ricoh.co.jp/dvd/asia/support/download/mp5125a/readme.html
1x to 4x DVD+R DISC COMPATIBILITY INFORMATION:


If a new 1x to 4x DVD+R disc is used in a MP5125A drive with firmware versions 1.38 or earlier, it may not be possible to set the output settings properly for the test-write area (the area where the writing power settings are made). In such situations, the following may occur.
- The process of writing to the disc cannot start
Also, if the writing power is set too high, the tracking servo may become unstable in the middle of the writing process, which could cause the following.
- Data written to the disc cannot be read

To avoid these problems, it is imperative that the MP5125A drive’s firmware be updated to version 1.51 prior to use with these new discs.


I updated the latest FW on my Memorex and I got no more +R ended up in the garbage bin.
I use BitSetter from www.DVDplusRW.org (+R and +RW as a DVD-ROM) and no more compatibility problem with any player.

At the end I decided to stick with PLUS.
I just love QuickErasing in EIGHT SECONDS.
And the + - media prices are almost the same.

Advice: Don`t do the Bitsetting with no disc or blank disc inside you get error message. Put a movie in or eject the tray.

Sincerely
tompika