DVD+R的燒錄表現比DVD-R好是可以理解的，這跟規格制訂優劣有關。如果同等級的DVD±R空片，DVD+R較佔優勢。

由於DVD+R規格提供燒錄機較多的訊息，所以一般而言，DVD+R可以獲得較佳的表現。

「Also a DVD+R(W) disc allows a drive to achieve better writing quality (independently of media quality), because it gives more information to a drive than a DVD-R(W). 」

http://www.cdfreaks.com/article/113



So maybe that's the reason.