Both dramas written by the same person. While they have different stories, the overall emotional feeling is a bit similar in my opinion. In both, the male leads live in lower life due to family circumstances. And on every episode, new plot twist will be revealed. The difference is that in BNNH the plot twists are more shocking/surprising, while TNH's are more subtle.
Both are very emotional and the core plot is similar. Bara no nai hanaya has additional lines around the story that makes things more complicated and exciting and some character developments are deeper and apply to more people in story. May be a little bit more serious emotionally but still heartwarming and lots of fun.