The pullover machine usually says it works your lats and from a mechanical standpoint that seems what makes the most sense. But, I do usually feel like I’m getting a good stretch in my pecs while I do them. When doing pullovers with free weights I think that it works the lats to a less extent because when you get the bar strait overhead the resistance on your lats stops whereas with the machine you bring the bar all the way down to your waist. Pullovers give your chest a good stretch, which would be beneficial to your chest routine, but it’s not a movement that puts a lot of tension on your pecs.