The bottom drawn system will gain a tiny bit more energy, since it will always have colder input in the heat exchanger, so a slightly bigger thermal difference, which aids heat transfer. (if all else is equal)
I think the most efficient method is to draw from the bottom, and always put the water in to the hight which has the same temperature as the input. There are many fancy heat storage tanks on the market, that do something similar, but they are mostly used in systems with different heat input levels. Like you have a natural gas heater and
solar collectors heating the same tank. The solar collector will draw from the bottom, and put hot water in the middle. (as it is likely just warm most of the time) While the gas heater will put hot water to the top side of the tank.