I read an article on Charles Poliquins website a while back that said let the reps dictate the load every set.
It said that if you have a rep range of say 3x6-8 reps and you can get 9 reps on the first set, increase the weight by 5 pounds for the second set.
If you get between 6 and 8 on the 2nd set keep that weight.
If you get 9 again increase 5 more pounds for the 3rd set.
How do you compare this to straight sets of less intensity of say 3x8 all with same weight?