There are a few scientific differences in Bodybuilders and Powerlifters: Strength and Power Training: Physiological Mechanisms of Adaptation. Exercise and Sport Science Reviews, American College of Sports Medicine Series. 24: 363-398, 1996.:
*Bodybuilders have a higher ratio of oxidative enzymes in Type IIa fibers over Type IIb fibers.
*Bodybuilders have a higher capillary density.Believed to be due to the higher levels of lactate build-up in training.
*Bodybuilders have a greater lifting capacity when working at a raised lactate level.
Observing bodybuilders at my gym, They work with lighter weight and higher reps to failure, it seems they are conditioning more their Type I fibers (type II fibers are 20% larger than type I fibers, hence give best reponse to hypertrophy)over their Type II fibers fo hypertrophy, as we know slow-twitch fibers are the first muscle fibers to be recruited in movements that demand small force, and the fast-twitch fibers are increasingly recruited by increased force demands, there is also evidence that type II fibers can be activated without activating type I fibers by heavy loads. Because the majority of heavy training results in hypertrophy of the type II fibers, powerlifters have a larger portion of hypertrophy in the type II area than when compared to body builders (in fact, powerlifters have very beautiful muscles, many of them just do not take very good care of their bodies). The point of any training regimen should include:
1. Resistance training
2. Flexibility
3. Cardiovascular fitness
4. Good nutrition