The main character: a poor girl who was kicked out by a mean mother. She welcomes a grandmother with dementia, she meets her "arrogant" grandson (not so arrogant in MOO) and you know what follows.
In my opinion, the acting is better in Shining Inheritance but being a family drama gives My Only One a good point. Each character has its own plotline (though everything intertwines somehow) instead of one couple solving everything (SI).
Careful, My Only One is pure makjang while SI emphasizes more on business.

Same cast ! I think George Hu and Annie Chen's chemistry is way better in Love, Now. Plus it's a rom-com.