It's about efficiency. BP-Revo was most likely running his setup at a lower efficiency level, and 5s bumped it up. At least that's my guess, anyone else is welcome to take a stab at it.

I'll admit my previous gearing was a bit short so that I could take it easy on the ESC. I guess now its just so much power I'm giving it such little throttle that current has dropped considerably, and thus, temperatures as well. I am convinced that voltage is the key to having a powerful cool running system...