The 1300a - we have 40+ at work (now some newer models inc. Sony's - not my choice!). I have one (1300) in my PC here - burnt approx 300 dvdr's, still going strong. The work nec's and mine started with a mix of NEC 1.04/1.05 fw, now upto 1.1b (is that right, the latest whatever that is). The officlal NEC firmware is now not bad - although not as good as some of the 'tweaked' firewares.
The NEC's have always been fine on +r, but a range of -r has met with bad burns (cannot read areas back - red as well as yellow, and yes, I know about the reading quality of these drives compared to others), especially with lower quality media.
I always use +r TY, verbatum +r, and a mix of TDK/Fuji +rw. Never a problem. However, at work, mostly where clients are concerned bringing in their own media - a mix of readily available -r discs cause no end of problems - no problem (in the main, allowing for cheap and nasty +r) with +r media. You have no problems - great!, our experience is the NEC 1300a loves +r and if tempermental with -r. Not once, but always the case - a bit better with post 1.0(a) firmware - not much better with 1.07ish. I always thought this was due to the +r camp being smaller, therefore the media made to more exacting standards, whereas upto a year ago, much of the -r media was nasty cheap ritek, cmc, bulkcrap, etc, media, dime a dozen made for a price - (+r was much more expensive). Whatever the reason, we soon moved to +r as much as possible because the NEC's were too much trouble with cheaper brand -r's - maybe not eveyone's experience - but we lost enough time trying to get things working as best as possible.