I have seen some swing yarders in the US and they tend to run skyline and gravity with motorized slackpuller, but I know about a few have been using grapples (for example Weyerhaeuser) in recent years. I think both Jeremy70 and me uploaded videos on Youtube of Dahlgren using msp on an 124 and also Jeremys videos of Vannatta using grapple on a Skagit GT4.
I also saw the Lake Lemare Logging's 144 on Axe men and was very surprised that the experienced operator never had used a grapple before, in BC I mean, since 95% of the swing yarders I have seen in BC have been running grapples.
The difference between US and BC has something with logging road density and construction regimes to do, log size (old growth/second growth) and of course culture.