Both approaches work as long as you do reps until failure. You should figure out the max weight you can handle while doing a proper lift. (Deadlift, squat, etc) and work to do about 8 to 10 reps at 80% of your max lift. As you get stronger you can keep the reps the same but increase the weight. For increased hypertrophy you can follow your 8 to 10 rep set with another set of 50% your max weight until failure. There is no point using very heavy weights to train since your form is poor and risk of injury greater