I really enjoy the historical dramas because I find their culture and language fascinating. The clothes, the makeup, the laws, the politics, the ways of life and the different honorifics and manners of speaking are so interesting! But I must agree with @Lost_in_the_Dream, the plots definitely feel similar especially if you watch two in a row. But I mean it kinda makes sense that they would feel similar because the plot has to fit into all the elements of the past that I mentioned above--there is less room for innovation because the future is already set (it already happened), if that makes sense.
The modern ones, in comparison, can be so much more diverse because there are many more elements to present day than there were in the historical drama days. I voted that I love both because to me they really balance themselves out. If I am starting to get bored or frustrated with present day ones, then I watch a historical one and vice versa