A) 1d mk iv (1.3x frame) @ 16 mp using a 400mm 2.8 II = 520mm

VRS

1dx (full frame) @ 18.1 mp using a 1.4 extender with same lens = 560mm

Which one would produce better results (sharpness, reduced noise, all the good things) for large printing?

Any advise would be greatly appreciated.
Scott