Not really similar apart from the body switch if that's your thing, with the added humour of a gender swap as well. Plus, you know, the great Hyun Bin.
If you liked the cat and mouse playing serial killer aspect of the show and you don't care if it's straight or BL than both dramas are for you.
They are obviously different, but the main actor is the same and with a similar vibe of an unsociable brainiac. Personally, I like his acting style.
While there are a lot of differences between the two dramas, the obsessed ML and the overall craziness are very similar. They are both dramas for people who can give themselves over freely to wild and funny plot lines, while leaving reality and logic behind for an hour.
Both deal with the ML falling for the FL he grew up with, one with an age gap and one without. In both it's the guy doing the chasing though My Fated Boy is much longer and not meant as a light web series.
A cold man meeting and reluctantly falling for a warm and quirky woman. And there is the thing with him calling her baka/idiot in both dramas - apparently in Japan it's a sign of a great romance...!
The story and tone are completely different, but the making of food in ancient times is the same, so it's for anyone who enjoys the food porn.
The tone and personalities are different, but it's still about a cat falling for a human, plus the whole childhood connections thing.
Both are a romantic comedy about an arrogant boss in denial of his feelings for his worker. Both have these bosses face the reality of her wanting to have a life and to date other men and both have a childhood connection between the ML and FL.
The rich younger brat with Daddy issues vs the older, poorer and responsible guy with the muscles! The setting is completely different but the overall theme is still going strong.