New research suggests lighter loads can be just as effective, but with lower risk of injury than heavy loads.
Personally, my experience agrees with the results of the study. I find that the secret to building muscle is to lift on a regular basis. The amount of weight doesn't matter so much.
POG OS. 368 SW, 12.54" balance, 21.0 MgR/I.
Problend kevlar 16 / Prestretched SPPP 17, 72/50 lbs.