Its so subjective and there are hardware realities to consider as well. I've started looking at render engines like Cameras. Some people like to shoot on Canon, some like to shoot on Nikon, some prefer...... I think less about tests of seconds but which one feels better and is more instinctive to me. Corona is this hands down for me - easily the easiest render engine I've ever learned and great images right out of the box. But I don't do animations, or heavy vfx, or characters, so it's going to be so different for everybody and I don't pretend to think it's the best solution for anyone else. Without the render wars, though, we would still be yelling at random strangers online about mac vs. PC, pepsi vs. Coke, or the z-brush interface.