Since I watched both the Chinese original "Go Princess Go" and this Korean remake, let me comment on some similarities and differences, and why you should watch both :)

1. Completely different storylines
Other than the "modern playboy's soul enters ancient queen's body" setting, everything else is redone. The Chinese drama was in the early webdrama days and featured an imaginary ancient time, while the Korean actually corresponds to one of the real kings in history. The Koreans took this short-lived king and remade him into a different (more interesting) character in the drama, and based a lot of clan feuds / political conflicts around this time period. This is very different from the Chinese drama, which had much less politics and much more just pure slapstick comedy.
So if you're into period dramas, this one will give you everything you need -- history, politics, as well as a very gripping fight for what is right.

2. AMAZING costuming and set
The Chinese drama was made in the early webdrama days with obscenely low budget, so they took the low budget and made it into one of their jokes. They had one electric fan to do all special effects with, they didn't have money for realistic costumes so they remade a lot of modern dresses, and the set was just ???
(That is not to say the Chinese drama is poorly made -- as I said, they took the low budget and they ran with it; and they made SUCH A FUNNY DRAMA from it that the historical inaccuracies can be ignored)

This Korean one, on the other hand, is made with a standard drama budget, so they really made the whole scenery so much more exquisite. Standard period drama costuming and accessories, and standard period drama sets... etc. Pretty clothes, pretty backgrounds -- what's not to like?

3. The comedy is just as existent!
You'd think that with the politics and the real costumes, that the Korean drama would be much more serious and boring. Not true. Thanks to the scriptwriters' cleverness and the actors' amazing acting/adlibbing, we got just as funny of a story (if not more so). From the wild (history-friendly) re-explanations of common modern words in the "Queen's Dictionary" to the facial expressions and physical comedy, Mr. Queen will have you laughing on the floor and screenshotting all those ramyun references :0)

Basically you can treat Mr. Queen and Go Princess Go as two completely separate works. Both have their perks and charming points. Both are entertaining to watch. One requires a little bit more brain power than the other because of its extra enriched storyline (Mr. Queen), but the complexity is also what made this drama do as well as it did.