Both are republican era dramas.
Leads in both dramas have a kind of forbidden relationship.
Revenge is the main theme in both dramas.
Lot of push and pull between the ML and FL.
In both the dramas after separating in the start the ML's face lots of hardships in the military and come back as a commander/person with high rank and also in both dramas after separation both the FL's face a lot of hardship.

Both are costume dramas having the same main leads.
Both have the main leads being in a situation of forbidden love.
In both dramas the main leads have other people courting them.
There is some love hate relation in both dramas.

If you love Ahn Bo Hyun's dramas then this is a must watch for you.
In both dramas he plays as the son of a rich family.
Both have good amount of comedy.
Seeing Ahn Bo Hyun in this series, you will definitely love the different side to him in See You In My 19th life.
Both dramas have smart and badass female leads so it will be fun to watch the main leads.