The latter. The question is, do you want to overly fatigue yourself on lesser sets? Assuming you are working up to a certain weight, with your final set being the heaviest.
This is starting to fall into different training theories. Neither way is right or wrong, just depends what you are trying to achieve and the way the program is to be followed.
Speaking from personal perspective, grinding reps tend to have a significant impact on the exercises that follow. Not ideal for me personally when I'm trying to move as much weight as I can for as many reps as desired.
EDIT: with that stated, I'm not totally against them neither totally for. I actually incorporate them in most of my exercises.