Longevity: DVD-RW versus DVD+RW

[dbminter]

Is it just me or does it seem like you get more rewrites out a DVD-RW disc versus a DVD+RW disc?  I realize there are various factors involved, such as the MID and the maximum write speed, but it seems I've gotten more rewrites out of, say, a 6x Ritek DVD-RW versus an 8x Ritek DVD+RW.  I was just wondering if there is actual concrete data that says DVD-RW lasts longer versus DVD+RW.  Thanks!