As Drew noted, there would be no shooting advantages in one gun over the other assuming gun weight and stock dimensions are similar. The stock of the 20's era R framed gun will likely be slimmer in the wrist, and the Marlin era gun could have the Single Sighting Plane, or raised solid top rib (a feature not available in the 20's); but there are very few visual differences between early Smith guns and those produced by Marlin. As FYI regarding R and FW Smith gun frames, the R frame was phased out during the late 30's and there's no record of Marlin having ever shipped any Smith guns built on the R sized frame; although they did supply replacement R framed barrel sets and other service related parts.
