This early 90s drama special depicts the same characters and time period, from the Korean perspective.
Jang Nok Soo is similar to Jang Hee Bin because they're both villains who lead the show, they're both palace intrigue dramas and were also competing for viewership in late 1995, being in the same time slot.
West Palace is similar to Jang Hee Bin because they're both palace intrigue dramas based on Joseon's "secret histories",and both were direct competitors when broadcasting in 1995.
It's almost the exact same story, despite a completely different tone (and time period) - being more accurate to the book, Love in the Rain is darker and more melodramatic than Romance in the Rain.
The same story, but with better production. Also the ceremonies are more detailed, some procedures and costumes are more accurate (although they still use hairpins and let Bins use dragon motifs). More on-location shots instead of everything in-set.
King and Queen has the same writer, covers the exact time period with the same historical figures and even some of the exact same scenes, but focuses more on the time period than on any one character. Also Queen Yun is her correct age in this one and not like 9 years older