The dust extraction is OK, but not great on the Hitachi. It has one good thing going for it, in that its dust catcher moves with the saw blade, like the Kapex does. On the down side, it has some odd blade stop at the end of the slide. I don't know how to explain this well, but it's a plastic piece mounted near the saw's bevel pivot hinge, facing forward, where the blade can "dock" into at the end of a cut. I have no idea why the have this odd thing. The problem is that when you slide the blade all the way to the back, the dust chute hits this and flops up/out of the way, and you no longer have that chute directing dust to the vacuum port (what where they thinking?!?!?). So, I cut that damn thing off soon after I got the saw.
I have been experimenting with dust extraction enhancements, which I hope to achieve 95%+ extraction, but I am not at a point where I can share info that's useful to anyone.