Julie_Know

They are both historical drama's with a heavier undertone. In both stories people get slowly pushed apart because of their own trauma's and circumstances. Sometimes there are no right choices, but you have to choose to achieve anything. Trauma's, losse, romance and trying to find yourself in flawed surroundings are the main themes.
They also both have many impressive (bloody) fight scenes.
(The romance in hongrang is slightly more on the foreground, fighting slightly more in my country)

They have a very similar vibe: very intense, people get hurt, you can really feel the chaos and stress of the characters who are just trying to survive. Choi Woo Shik plays in both too.