I'm gonna quickly chime in.
Higher volume coupled with lower weights is good for a metabolic type of training. You affect Type I, or slow-twitch, fibers that possess slower twitch speeds and are relatively fatigue resistant.
Lower volume coupled with higher weights is good for Type IIa fibers, or fast oxidative that are less fatigue resistant.
This is not a conspiracy. You can search on PubMed. It also works nicely for naturals. Or should I say 100% lifetime, non-provoked, full-scale natural?