In addition to the different focus distance there is also an eye relief distance difference between a pistol scope and a rifle scope. A rifle scope is for three to four inches of eye relief. For a pistol scope it's much greater.
Steve, stay with the pistol scope for the reasons you listed about parallax. Especially since you already have a very good pistol scope. Why spend the money on a new scope when you already have a Leupold? Looking at your posted picture, you could probably move your scope forward 1-2 inches, still have plenty of eye relief & give yourself a little more hand room for pumping. Just a suggestion.