Both of them are based on manga and have marriage as a main topic.
However, the main leads personalities are very different.

Both of them are based on Josei mangas. While "Please Love the Useless Me" has a more funny approach, "Hapimari" is a bit more serious. Both of girls are in a difficult financial situation and the main lead help them.
Also, Dean Fujioka is the main lead in both of them!
Enjoy :D