well my imagination is since a duel (battery on battery) would be quick now (because of fire-control computers etc.), a rate of fire would likely be the decisive factorIf you are under that you are probably a little to excited to start counting how many shots you are taking.
Again rate of fire in this is a bit of a fictional reality. Yes you can hold that more consistently with a mechanical loader but what are the chances of ever needing to shoot that fast?
One two rounds okay with modern ammo and fire control you can even drop them both on target in the space of a second or two.
'one round too few' if you know what I mean