Well in the long run each has its advantages and disadvantages, but one choice is probably as good as another, well except one handed no shield, but I doubt many soldiers would run out on the battlefield with a one handed weapon and no shield if they had the choice (well before the advent of firearms). As far as I'm concerned the history of warfare is about powergaming, always trying to devise the most potent defense against the latest weapon, or trying to devise the most efficient weapon for breaching your opponents defenses, this is the reason that there is such a tremendous variety of arms and armour.