Both are happening in the same time frame. In both Kim Sang Kyung and Kim Yeong Cheol are playing the same characters, Kim Sang Kyung plays king Sejong and Kim Yeong Cheol - king Taejong. In The Great King Sejong Jang Yeong Sil is an important supporting character, while in Jang Yeong Sil he is the main character.

Both drama are about reporters and revolve around ethics of the reported news.

both deal with questionable police practices, also in both the main leads have some sort of dark secret.

Both main male leads are the self-sacrificing sort that have more lives than a cat, both are in love with a childhood fried who is the source of at least half of their troubles.