there is a difference in reliability but the difference between a +R and a -R is not related to the dye layer in the disc.
The difference is a mechanical one with the configuiration of the "pits" and the location method.
a -R uses data space for file location
a +R the location is a pressed in component of the pregroove.
a -R user "prepits" to locate the pits.
a +R doesn't have prepits and the pits themselves are larger.
IF you EVER do multisession a -R disc requires a LARGE leadout and lead-in between disc data sessions, this is on the order of 70Mb-90Mb, even if the final session is the last one on the disc.
a +R disc requires only about 7Kb of "lead out"" between sessions.
if the quality of the discs is EXACTLY THE SAME, the +R are better
I'm not prepared to claim that the difference between a +R and a -R is greater than the difference between a Sony labeled "Mystery disc" and a T-Y produced disc, but there is no question whatsoever
that two basically identical discs the +R is better.
However you'll only ever see that difference if you compare two discs with identical scratches.
the +R are more readable with a given level of scratches.
+R are basically the result of several years of additional research.
as for getting discs from an open spindle pack?
either buy your discs from somewhere else, or buy enough at once that you can get a sealed pack.
I have several sealed 100pack spindles of Sony labeled DVD+R's
Right around christmas time Staples had them on sale for $22.95.
(around 1/3 the normal price) I bought three.
they may not be the best, but for almost exactly 25cents each...
Over the counter retail price they are good enough.
I archive my mp3 library on DVD+R discs, but I make fresh backups every three months or so, and 90% of those backups is stuff I've already backed up and so far discs even a year old are still readable.