Both dramas have a similar feeling with dark, depressive tone, the characters are also very similar and in both dramas OST is really great. Mature dramas with very good actors and difficult storyline. I have enjoyed in both of them because I liked it that these are very different from all others typical Korean dramas with characters who are full of faults and where the chemistry between all actors is just amazing. A little note- What happened in Bali is much darker, tragic and more psychological that Que sera sera but definitely both of them are worth watching.
Both have friendship between male and female, in both of them the main leads are in love with each other just don't realize that right away and don't considerate each other as potential lover until some things have happened. The leads in both dramas are in their 30's with good jobs. The chemistry is amazing in both of the dramas and relationship so natural, realistic and through all show you see everyday problems which everyone of us with that age have. And both of them are great.