Both dramas are historical dramas with fantastical elements that stars Lee Joon Gi as the lead male actor. In Scholar, Lee Joon Gi is the more mystical character while in Arang, the love interest is the more mystical character. Actor Han Jung Soo appears as a “hunter of sorts” in both dramas.
Qualitywise, I find Arang and the Magistrate so much better, people should try Arang even if they find Scholar boring.

Both modern dramas of Lee Joon Gi. There are parts in both dramas where he lives in an identity different from his real one.
Actually the main reason I'm recommending Time Between Dog and Wolf is because I was most amazed by LJG in that drama. He's always amazing in almost all his dramas, but I'm most amazed with his acting in Time Between Dog and Wolf aside from Flower of Evil.

= Same lead actors as the main couple (I personally don’t find their chemistry the best in both dramas but the female lead is more bearable in Time Between Dog and Wolf than Gunman, perhaps because there’s a second more compelling female lead in Gunman).
= The actor who plays the real dad of the female lead in Time Between Dog and Wolf is the same actor who plays the dad of the male lead in Gunman in Joseon
= Father of a woman (female lead in Time Between Dog and Wolf, second lead in Gunman) who has a thing for the male lead is the one who killed one of his parents
= Male lead has two identities in both dramas, one before his supposed disappearances (death) and one after. His second identity is used to spy on the villain for the sake of revenge plus other things he or the organization he belongs to need to accomplish.

> Both are historical or at least have some historical parts
> Themes of reincarnation are present in both shows
> A murder mystery is central to the plot
> The supporting characters, especially the underlings of the lead guys, are very funny and are really great parts of both shows.

=> Shin Min Ah is so good in playing these cute mystical beings in an almost "impossible romance"
=> The chemistry between both leads are amazing
=> Male leads started out as somehow full of themselves but later grows as a character due to Shin Min Ah's character
=> One notable difference is there is no annoying rival female in Arang and the Magistrate, so you can watch Arang if you don't like those kind of characters.

> Same writers for both dramas (except Tree is based on a book by Lee Jung Myung)
> Two of the best historical dramas ever
> Smart protagonists and villains
> Debates and conversations on politics are interesting
> Great actors
> Shin Se Kyung is in both dramas

> Both dramas main female characters love painting.
> Kim Yoo Jung is in both dramas (she's the child version of Moon Geun Young in Painter of the Wind)
> Jang Tae Yoo is director of both dramas
==> expect some lucious paintings for Hong Chun Gi/Lovers of the Red Sky as they were depicted well in Painter of the Wind.
> Some instrumentals from Painter of the Wind also feature in Hong Chun Gi/Lovers of the Red Sky
> Trivia: Hong Chun Gi/Lovers of the Red Sky is the reunion between Jang Tae Yoo and Kim Yoo Jung 13 years after Painter of the Wind.
(PS: Painter of the Wind deserves a rating higher than 7.8, if this is a post 2016 drama, it would have gotten a higher score, at least 8.5).

They have the same writers. They main character is also a twin in both dramas. There is a prophecy about the twin characters in the drama that is important to the plot. They also both have complex characters, meaning likeable villains, protagonists with a dark side, and characters which we won't understand at first if they're good or evil

They have the same writers. They main character is also a twin in both dramas. There is a prophecy about the twin characters in the drama that is important to the plot. They also both have complex characters, meaning likeable villains, protagonists with a dark side, and characters which we won't understand at first if they're good or evil

Similarities
=> Historical drama starring Lee Joon Gi
=> Excellent action stunts
=> Main character's father died, he takes on a different identity to find his father's killer
=> Main character (aside from his main disguise), also used various identities (thus wears various costumes) to fulfill his mission
=> Main character becomes hero of the people along the way.
Differences:
=> Iljimae uses swords, Joseon Gunman uses guns
=> lljimae is set around 1600s, Joseon Gunman is in late 1800s, close to end of Joseon dynasty
In my opinion: Iljimae>Joseon Gunman, but both shows has their own merits.

1. Both dramas have Moon Geun Young's character having relationships with older men.\
2. Actually, the main reason I'm recommending Painter of the Wind is because it's such an underrated drama and more people need to watch it. Especially Moon Geun Young fans, Moon Geun Young showed superb acting skills in Painter and it is her work that made her receive a daesang and a baeksang award.
(Bonus: Park Jin Woo, Moon Geun Young's boyfriend in My Little Bride, also plays her same age rival student in Painter of the Wind).

Both feature two artists (one older and one younger) who eventually worked for the king as the king were impressed by their skills. Except in Painter of the Wind, the artists are painters, while in King and the Clown, the artists are male clowns. The two main artists in both shows also really care for each other and are willing to sacrifice a lot for one another. Homosexual themes prevail in both shows though presented quite differently. In King and the Clown, you have a feminine male clown and two other men (one fellow clown and the other is the king himself) who can both possibly be interpreted as having some sort of feelings for him. In Painter of the Wind, the younger female artists has lived as a man her whole life and the older male artist who thinks she's a man can possibly think of himself as homosexual since he is having some feelings for a fellow male artist. In addition, the female-pretending-to-be-a male artist in Painter of the Wind is also shows to have another love interest that can be interpreted as homosexual, that is her relationship and fascination with a female gisaeng