The dumbbell row isn't a good lat builder. Don't get me wrong. Rowing movements will hit the muscles of the upper back surrounding the scapulae, but you'll get more bang for your buck by using other rowing exercises instead of the one-arm row. This is because of the body's position relative to the dumbbell.
If you're going to do dumbbell rows, you can easily optimize the movement pattern to better hit the lats.
Use more of an arcing motion that "drags" the weight towards the hip and it'll hit the lats hard. It doesn't take a 160-pound dumbbell and a contortionist twist at the torso to make an exercise like this do its job.
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