at 40% and up, you have access to the highest drop table when risking 75K. at below 40%, you don't. At 40% and up, you have a higher chance of getting a better item that is not from the main drop table. At below 40%, you don't. That's basically it, 100% holds very little benefit over 40, except for the fact that you can PvP longer before you go back to getting drops from a less loaded table.