The loudest concert ever!!

Haven't been on so many conserts yet (for some reason, I'm not a that kind of a concert person...), but Iron Maiden in July last year was a sort of loud experience. The "gunfire" before Where Eagles Dare was something...

By the way, I've always wondered which is "better" for a listener's ears? An open air or a concert hall concert? In my logic, I think it's the open air, 'cause the sound doesn't reflect back from the walls, it expands instead and doesn't hurt your ears that much...