They´re both soft in the storyline and also tend to be more comedy than drama. "Oh! Boarding house" sometimes seems like a parody of other BL series/ stories. I think both are equally light and fun to watch.

Both have an uncomplicated storyline and a similar production. However, "OH! Boarding house" is better in the implementation of the story. Way better. The love story of the main leads both evolves around adulthood. I´d recommend "Oh! Boarding house" even if you didn´t like "Behind Cut".

While the concept of these two is worlds apart/ very different, they both result in having to survive at the cost of other lives, such as their friends. Betrayal is a huge aspect/part of both stories. Also, violence/ recklessness and failure of morals in both dystopian scenarios are similar.
However, Remember 15 contains more extreme gore.

While both Kdramas revolve around injustice and crime, the female leads are strong, unique and independend. Additionally, the male leads in both of them are rather imperfect and have a healthy amount of character development during the series. Both remain exciting until the last second.