Fun and Fitness: Are you looking to bulk up?
A split routine applies the principle of overload maximally. This basically means that the more stress that is placed on a muscle, the more it is stimulated to change. Split routines allow for multiple exercises for specific body parts, therefore resulting in maximal exhaustion/stimulation of all muscle fibres worked. The high set numbers ensure exhaustion and can elevate anabolic hormones. Seven days of rest ensures full recovery.
A full body three times a week routine is based on the idea that training is the stimulus for change. Theoretically, the more frequently the muscle is stimulated, the more likely it is to change. This is also based on studies that consecutive days training does NOT enhance markers of muscle damage (assuming that after 48 hours, the muscle cells are ready to be stimulated once again). A full body routine also allows every workout to include large muscle group exercises for maximal anabolic hormone release.