Who has the most powerful enlarger quirk, Yui Kodai or Mount Lady?
We don't know how much Yui can enlarge herself. However, there are two distinct points that make their quirk different.


Mount Lady only enlarges herself to 2062 cm. That's it. However, Yui can change her size as she wants. If her quirk has no limits (again we don't know) she might overgrow Mount Lady.
Yui also shrinks herself but that's not relevant for the question.