Honestly, a mix of both. To completely smash your nervous system and muscle fibers, you have to explosively lift as fast and as perfect as possbile. For instance, when I do squats, I come down normally, ass to the floor almost, and then I try to explode as fast as possible with as much weight as I can do for 6-8 reps. I first start with higher reps though and then pyrmamid down. Now, towards the end of an excercise I always incorporate a pump set, in which I do as many as possible and even get sloppy towards the end, pretty much until my body says "yeah, your f@#$ed up for doing this to me". Now, if your trying to bulk, the rep range is between 6-10 reps, if you are powerlifting, its more like 3-5 reps, after warming up with lots of rest in between. Its really what you are trying to accomplish, i mean, there is enough science behind whatever it is you want to do, just always put 110 percent, like its your last workout ever.