I don’t think buffer underrun errors are much of an issue anymore, or are they? At least not to the degree when CD burners first showed up. 2MB buffer is pretty standard. I don’t know how much of a real world difference having a larger one makes.
If I were you, the main thing I’d wanna focus on is the burn quality. Color of the faceplate, LED colors, buffer … they seem quite trivial if a burner can’t perform to the standard you’re looking for.
If you’re satisified with the general sense of the burns for particular media you’re targeting, then the overburning, overspeeding, etc … seems to be gravy.
I guess it’s a matter of perspective. But, I came into the DVD burning realm with the lure of burning a full DVD in under 6 minutes @ 16x. Then, thanks to this site, I learned quality of the burn is of the essence … ie. having a 6 minute dvd burn does me no good if it turns out to be a coaster, etc. So, now, I don’t mind waiting an additional minute or two to burn at 8-12x and give my chance the best chance for a high quality burn.
Just my $.02.