Boeing certificated the -400 with better rudder response than the Classic. Can you imagine a company like Boeing pumping up the engines and systems of the 747 and not bothering with making any improvements to asymmetric handling? In all respects, the -400 handling was vastly improved. Two engine out approaches went from being a crisis to a relative breeze on the -400. On the Classic, you were committed to hitting the ground, on the -400 the whole thing was far more civilised.