Several people have mentioned this overkill theory, and I'm not sure I buy it. What application is there that requires the energy of the .338, but the .50 is way to much.
If we're talking enemy combatants, dead is dead, it dosent matter how hard you kill them. I also find it hard to believe there is a hunting application for the .338 lapua. Its is overkill on game. For anti-material, the more damage the better, so use the .50