Are lat pulldowns as good as pullups?
If you can't do pull ups properly they are. Just like I am a genetically crappy bench presser, I am genetically good at pullups. For close to 30 years I was always able to do 20 or more strict pullups. Some dudes, particularly big, heavy dudes, hell, even big STRONG dudes have this problem. Because of their size or genetics, they just can't do pullups comfortably enough to target the lats. 6X Mr. Olympia Dorian Yates was hardcore to the bone. He got up to a lean 315 off season at 5′11″. He certainly could not do pullups and target his lats effectively. It seems resistance increases exponentially as bodyweight goes up when pullups are involved. He made manhandling heavy weights on reverse grip pulldowns in strict form look cool. He also had a barn door wide back. Fitness and muscular development are close cousins but aren't one in the same. If I want to be as athletic as possible I would do pullups. If I wanted the widest lats possible I would do reverse grip pulldowns with a heavy weight in strict form. Lower the weight slowly during the eccentric phase.
Here is Dorian and his obscenely wide back built with reverse grip pulldowns and barbell rows: The YouTube video below shows proper execution.