Performance however is hard to compare until you compare the same really complex scene with lots of lights and stuff in the different engines. If there are for example many subsystems running which are responsible for really effective culling and streaming and whatelse, the engine will be slow in a small simple scene, compared to an engine which really just renders everything, but this will change as soon as the scene gets more complex. Another big difference is the way things are rendered: Lightprepass rendering i very slow in a simple scene with just one light compared to forward rendering, but if you want to have more lights and more polygons and stuff, lightprepass rendering will turn out to be much faster than a forward renderer rendering the same amount of lights using multiple passes.
In the end the best engine would probably the one where you can turn things on or off, but then again, this would mean for the user that he needs to know, what everything is, which usually doesn´t seem to be the case.