[78-L] to DVD or not to DVD?

[Malcolm Rockwell]

Okay, is there a difference between DVD+R and DVD-R?
The internet is somewhat vague but says that both can be read by any 
late model computer. However, "common knowledge" (god, I hate that term) 
has it that DVD-R runs on a PC and DVD+R runs on a Mac.
In what model year will either of the formats run on the same computer?
I am completing a project and need to figure out if I need to retail it 
in only one or in both formats and, if in both, what percentage of each 
I will need to make available, say 75% DVD-R and 25% DVD+R, to be covered.
I realize this is not strictly a 78-L topic but data storage is within 
the realm of what we do, especially for lots of audio files (and others, 
such as JPGs) needing to be shared.
If it is felt this is too far off beam, please just reply offlist.
Thanks!
Malcolm