Thanks for bringing this up, I've wondered a lot about this as I also have a really tough beard. When I got my Hart razor, I thought it shaved so well just because it was a quarter hollow grind. But over the last few weeks, after comparing it with some of my other razors, it seems to me that it shaves so well (for me) because the shape of its edge makes it easier to make the shaving passes that work best for me. It has a modest smiling edge. I'm going to test this over the next few weeks to see if this is true, for me, anyway.