Originally Posted by Dave Fitzgerald

It enables a smaller flight controls, meaning less drag. Or, same size surface, more power. It's needed with a larger engine, as in the example of a rudder and engine out situation--hence the 777X. You could keep the same tooling for the rudder, size and shape with larger engines.

The question becomes ,is the smaller control surface worth the small amount of extra weight by putting in the system and maintaining it?