Currently I think there are two thoughts with multiple rep deadlift lowering
School 1 says explode off the heels as hard as fast as you can, then let the weight fall at the top portion of the lift, and immediately get back to the butt down position to explode again.
School 2 says to slowly ease the weight down, then come back up once the body and weight are in position.
School 1 will probably allow you to get more reps, while school 2 will probably tire you out, but activate more muscles.
Which is the better way?