I'm not the biggest fan of neither but whoever believes Zoro versus King was better is fooling themselves. Luffy versus Katakuri had themes matching both the fighters's own struggles and the field, character progress, some superb panels and an emotional ending. On top of this, Katakuri's gimmick and how to overcome it actually made sense (sees the future > opens holes in his body > Luffy develops future sight to counter Katakuri's > uses a speed-based form to overcome him with speed being a well-established counter to observation haki) while King's was totally random and remains vaguely addressed.
It's miles away, not even debatable. Luffy versus Katakuri had narrative effort behind it; Zoro versus King was empty and lazy.