total body or body parts

Which is better, do a total body workout three days a week or one part in one day really hard once a week?

Research has shown that best results for muscle growth and strength increases come from training each body part 2x per week. The key is to not repeat the same exercises each time , however to use different exercises that place different emphasis on each muscle group. For example, lets say you do back squats for legs one day. The next time you do legs that week execute front squats. These two movements although both are Leg exercises each one places a different emphasis on different muscles in the legs. The Back Squat places more load on the glutes and hams, while front places more on the quads.