Admittedly. I think I should know this but I don't lol!
as far as building power and strength goes they're two different things and you can tell a powerful movement from a slow strength movement pretty easily. However, say if I did a set of 5 deadlifts or squats etc. Reps 1-4 were fairly quick and 'powerful' but 5 was hard and considerably slower. Would rep 5 as a slow rep still be beneficial for building power or should I call it a day after the fairly speedy 4th rep.
Similarly would a 3 rep set of slow heavy reps still build power? After all I would be executing them as quick as I can even though they appear slow.