A 12" arm with its shallower arc is like a linear tracking arm that is set up wrong, it is wrong over larger parts of its travel then a shorter arm. I don't hear the difference the math claims but I do a very precise setup.
My 12" 3D arms when set up properly have the smoothest upper midrange I have ever heard, rivaling the best linear tracking air bearing arms. The one piece totally damped design with no small pieces sticking out all over really does not resonate and that makes a uni-pivot work even better. HW