I have one I use quite frequently as a belt knife around camp. I love mine. It's a very well though out knife and some things I didn't pick up until after handling it a bit like the first inch of spine is squared enough to strike a ferro rod but the rest of the spine is rounded which makes it comfortable to whittle with, and the choil, while not a designated finger choil, is the perfect place to put your finger when you use the knife to filet. The coating picks up dirt quick, but a quick clean and it will look brand new after a wash every time. The handle is also super comfortable, probably in the top 2 I've ever handled. The only thing I would say is that as a bushcraft knife thin the edge when you get it as Spartan Blades come with pretty thick edges but it makes sense for the intended purpose. I re-profiled mine to 20 degree per side and it makes a great knife work even better. My only knock on it is that the sheath does leave you wanting.
There's also something to be said about pride of ownership. People can talk all they want about how expensive something is or, "This $20 knife will work just as well," but there's something about having that blade that you want, that connects with you, that makes the experience of using it just that much greater. The fact that Bill Harsey hand grinds each one just adds a personal touch to the knife.
The Duke also looks like a great knife and since I don't have one or haven't handled one I can't comment, but I've always liked the design. I'm sure both would serve you well, choose the one that calls to you brother. If you don't have to which it sounds like you don't, never settle.