Gunman in Joseon (2014)

Both drama's story is a little similar because in both of them the MC goes overseas and comes back with a different identity.

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.

Both of the main characters decided to adopt a new identity and embrace western culture. Also, both characters use guns... a lot. I guess those are the things that make both dramas similar.

Both dramas are set during the reign of King Gojong. This means that the drama is set during a time when there is such a great transitional change going on in Korea (late 1800s). Korea, a kingdom known for being against the influence of foreigners (except maybe China or Japan) is shown to starting up to open to Western influences in both dramas, thus we see the lead characters use the gun more instead of the traditional swords (though some characters still use swords). We also see how Western influence is impacting the main characters. Example is how both female leads in both dramas got fascinated by the western objects they encounter in the show. We also see some men cutting their traditional long hair to fit to a shorter western hair, plus they also trade their hanboks to western suits. Big difference in setting is that Gunman in Joseon was showrn during Gojong's earlier reign while Mr Sunshine was during his later reign.
The character of Lee Joon Gi in Gunman also has similarities with both the leads in Mr Sunshine. LJG character and Lee Byung Hun's Mr Sunshine character are similar in that they suffered a lot in Joseon before they left for another country. Using an identity from another country (LJG using a fake Japanese identity and LBH becoming a US Soldier captain as US Citizen) and wearing Western clothes, their return to Joseon will lead them to more hardships to overcome before eventually becoming heroes to Joseon people. LJG character also has similarities to Kim Tae Ri character in Mr Sunshine. Both parents died, and both became masked vigilantes who do missions which eventually helped Joseon.
Basically, both dramas are about how people lived, survived, and even become heroes of Joseon in a time of impending change

Same leading actors, a somewhat similar plot-line - JG is historical while TBD&W is Modern - TBD&W is the better drama in my opinion.

= 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.

They are both set in the Joseon era
They are both dramas worth watching.. if you liked one then you should definitely have a go at watching the other.

Both take place in the 19th century Joseon, when the Japanese invaded Korea. ML is fighting for justice and for the weak and poor, just like they are fighting the system in The Nokdu Flower.

ML starts out gentle and kind, then his family is stolen from him, he is presumed dead, and his personality shifts into revenge and hatred for those responsible. He returns and reunites with FL who helps him heal/reunite with what's left of his family. The tones are similar and both have happy endings despite being darker stories.

Both dramas are about the main characters hiding thier identity and carrying out justice during a politically turbulent period in Korean history.

Very different plot but better story. Way more complicated in all kinds of ways, longer, sadder, worst?
Same actor: Lee Joon gi~ but acting all the other way different. Em, dark prince? Probably suits him more.

Lee Joon-gi in another period piece doing what he does best by bringing the titular lead to life.

Park Yoon-kang is the son of the last great swordsman of the 19th Century Joseon. After the murder of his father and the enslavement of his younger sister, Yoon-kang trades his sword for a Western rifle on a revenge mission to find his sister and those responsible for destroying his life , but he ends up becoming a hero for the people as he fights corruption and his own inner demons.

Lots of action and romance with strong characters both male and female.

While one is Chinese and the other Korean, both are revenge dramas set in about the same historical era. The ML (or one of the MLs) is shot and assumed to be killed but returns claiming to be a different identity and from a foreign country. Because he has the same face, people who recognize him try to test him, but he lies about his identity, even to the FL who he loved.