I would love a 19 made in 1959, that would be a birth year, favorite model gun for me. It seems that you would like to free up cash for future purchases, and you like the trigger on the 15 so I assume you shoot it, therefore for you sell the 19 as it's value is far and away higher than the 15, and you don't show any favoritsm for the 19.
If the guns were mine you would not be able to buy the 19 from me, only my estate. Make sure that you price the 19 appropriately, no dash 19's do not show up much, and are pricey when found.