Deads are the best. It has been shown that pulldowns with a narrow grip or reverse grip are in fact much better for lats than a wide grip. The wide grip thing is a myth if you ask me, it mainly will work your rear delts and the muscles really high on your back. If you want lat width, a narrow/medium grip will give you the longest ROM. I would choose barbell rows over DB's unless your gym has really heavy dumbells. I need at least 150's at a minimum to do a decent set of 6-8, and I'm afraid to say not many gyms go that high.