For smoothness, as opposed to lightness, my best DA revolver pull happens on an old mid 1970's vintage M-28. N-frame cylinders have more polar moment of inertia about the ejector rod, especially M-27's and M-28's with smaller chamber holes. More of the DA pull effort is devoted to spinning the cylinder on these guns and less to the rebound slide and hammer. Lot of mechanics there, but that's my theory why this particular wheelgun DA cocks so smoothly. Also, a narrow non-target trigger masks minute discontinuities in the force-distance curve. I have an example of very nearly every numbered S&W and my old M-28 is the smoothest of all, smoother than my Colts as well. You can really feel the difference when SA cocking. That big cylinder almost spins itself once you get it turning.