I prefer K-drama, as they look more cinematographic and have better production value.
C-dramas always have tons of filters that make them look cheap. All faces look super pale, and usually, the color grading is off, with overly bright images. It burns my eyes.
There are a few exceptions, like some thriller C-dramas, but most other productions have these horrible unnatural filters. The dubbing is also annoying and make for very cheap shows (minus a few exceptions).
Also, Cdramas are usually more predictable due to the censorship they have to pass (bad guys never win, no controversial topics, government workers are always honest and helpful, etc.)