User blog comment:Kaido King of the Beasts/Chapter 879: Mirror Battle in Mirro-World/@comment-27930128-20170922112820/@comment-24850639-20170924145855

My personal theory is that Katakuri made a grave error in judgement when he said that there was nothing with Luffy's devil fruit that he couldn't do as well. At the end of the day, you have to look at the natural properties of Mochi and Rubber. Katakuri's mochi can't actually hope to match the natural (unlimited in Luffy's case) elasticity of rubber. The elasticity of rubber is essentially the basis of Gear 4th, combined with haki, which Doflamingo explained during his fight with Luffy. Mochi can't generate raw power from extension and compression like Rubber can, I think Katakuri is just augmenting it with his own physical strength and ability to produce unlimited Mochi. Will glady eat my word if Katakuri manages to tank a King Kong Gun or Leo Bazooka even, but until then I protest the note on the Mochi Mochi No Mi page that it's naturally superior to the Gomu Gomu No Mi.