At this time, you might be tired of discussing the novel/drama and the depth of the main leads' feelings and characters. Well, I'm still there:)))
I am watching the "Stand by Me" modern (around the year 1996) drama mostly in the school environment. (In this drama, I have to say that the FL is so powerful in showing every bit of her feelings. One of the best female performances this year. Then the ML, he is the same. ) It reminded me of the love stories of XY/Jing, XY/CX, and XY/XL if in modern years. FL has deep feelings for both her best friend (poor, wise, hardworking,...) and her bad boy (shown that way) attractive, rich friend. Both have big baggage and are in love with her, but can't or don't want to confess and reveal their love for her. She has a more passionate attraction for the bad boy but a deeper feeling for the other one... In the end with all the ups and downs in their relationships (not there in the drama yet), she chose the bad boy. Why?
With all that discussed here for the reasons, I'm still thinking about why XY chose Jing and not XL. By watching the drama mentioned above, I could see why. On top of what has been discussed, I found it in Jing's courage(this one is so hard for him to grasp), persistence, and honesty in front of his love. From early on, despite all the obstacles, he brought XY into their love story brightly (starting with the 15-year waiting promise) and tried patiently resolving the problems. Although XY stopped doing her part after FFYY pregnancy first, later she worked with Jing to overcome the problems. They teamed up actively for the sack of their love, which CX and XL didn't do.