Dual Citizenship, China L visa questions

Hi, I have dual citizenship - South Korea and the US. Which one would be easier/cheaper to apply in the US? (I am currently living in Los Angeles) Also, if I apply with my korean citizenship, what other documents would I have to submit? (Will they need a copy of my US passport? Or proof of residency in the US? I am a student here so I guess I can submit my acceptance letter?)