I've always wondered about this one. To me, both genres sound about the same. I've always considered NWOBHM bands as just traditional metal. For example, Iron Maiden and Saxon are considered NWOBHM while bands like 80s Judas Priest, Dio, and Accept are considered just tradtional heavy metal. So what exactly is the difference between the two genres? Is NWOBHM as a genre generally faster than traditional metal, but not quite as fast as speed metal with a slight punk sound, or is NWOBHM nothing more than a movement of bands from the late 70s-early 80s that were from England and played traditional metal? The only noticeable difference I see between the genres is that NWOBHM is slightly fatser with more of a punkish vibe to it. Even so, I've always considered NWOBHM and traditional heavy metal the same thing.