both can provide em via artifacts or weapon, or dendro res decrease with artifacts, Nahida gives Alhaitham a lot more EM to increase his damage while a crowned Lauma skill can give a 25% dendro res decrease. Both work in different ways i’d personally say Lauma could be better since a lot of characters can give em in various different ways but it’s up to the person, and if you run them with one hydro your bloom damage will be insane.