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.
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.
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.