Large ships are significantly more cost efficient, given the reduction in crew redundancy, however they are much harder to defend. The Japanese made this fatal mistake during WWII. Large, poorly defended Japanese ships became target practice for US torpedoes.
The US can build large ships because they have the nuclear deterrence and mobile missile defense systems to ensure their carrier's security. Thereon, they can consider cost efficiency. If America's adversaries all had the same number of nukes that the US had, American carriers would be much smaller than they are today.
Given China's current missile defense immaturity, it would be a terrible mistakes to build larger, less defensible ships