LED Intensity

[Aquattro]

A question came up in a different thread, asking why almost everyone runs their LEDs at less than 100%, often much less. Why is that?

Does it not make sense, mathematically, that if I run 4 lights at 50%, I can get the same results with 2 lights at 100% ? Sure, coverage is a different, but lets say 3 lights, higher up but brighter, doesn't that do more than 4 lights at 60%??

So what do you run your LEDs at, and why?