Oops, I lost this thread. Thanks, Chef, for bringing it back. Hopefully, Ang has made decisions by this time.
I think the consensus opinion agrees with Chef - "no significant difference" in PLUS or MINUS R disks. Some folks argue that the PLUS R research and manufacturing is giving those disks better lifespan because of better component-chemistry.
(A multi-session recording - "I burn some files on this PLUS R disk today, then I set it aside, and next week, I add another set of files to that same disk, filling it up with several 'burn' sessions." Like a floppy disk, therefore.)
Originally, PLUS R's suffered from a reputation of incompatibility - "I burned two sessions onto this PLUS R disk, but my other computer can't read it. The burning computer can, but this second computer can't."
This "incompatibility" might have been the Burner, it might have been the Disk, or it might have been the Software Version OR the User's knowledge of what he was doing.
The end result was the same, though, and PLUS R's didn't get a huge acceptance. And there were a lot of 1st-Generation TV DVD Players that didn't recognize PLUS R disks - which were indeed '2nd generation' media.
I think it would be tough to find a working 1st-Generation TV-DVD Player now that didn't 'see' PLUS R disks properly, though.
If I had questions about my own equipments' compatibility, I'd buy a 10-pack of PLUS and MINUS disks, and see if there was any Play-Read compatbility issues across any disk-reader I could find. It won't make much difference to the burners in a PowerMac.