Rows vs separated rear delt/upper back work
As a general rule, you want the muscle group that you're targeting with an exercise to be the one to fail first (if, of course, you're going to failure).
During a wide-grip, upper-back targeting, row, you are performing scapular retraction with the upper back, horizontal abduction with the rear delts, and elbow flexion with the biceps/brachialis/whatever.
Anyone of these muscle groups could fail first, depending on the person (IME my rear delts fail first), resulting in a lesser stimulus for the target muscle group (i.e. the upper-back).
Would it not then be more sound to target each of these muscle groups with isolations instead for a greater individual and therefore total stimulus? For example, a kelso shrug, a rear delt fly, and of course a bicep curl.
And obviously this is a small effect and you should just train hard and you'll grow blah blah blah... But I just wanted to prompt a discussion and hear people's experiences.