My personal opinion is ofcourse with the compound lifts. I do bi's ofcourse on back day. I hammer my back then finish off my allready fatigued bi's with three quick movements. 3 sets of straight bar, 3 sets of standing DB curls with a weight that lets my bi do all the work then 3 sets of either close grip preacher OR 2 or 3 sets of the ronnie coleman camber bar crazy curls he does, (5 low, 5 high, 5 full range). All sets to failure and I dont use ridiculous weights.
These 8-9 sets for bi's are no marathon. Its quick with almost no rest between sets. Takes 15-18 minutes tops. All this ONLY after really heavy BB rows, super heavy rack pulls, and heavy wide grip pull downs and one arm machine rows if i am in the mood.