*WARNING: this post is full of spoilers*
OK, I've fast-forwarded through the DVD-Rip.
Here's my conclusion:
-The Tartan contains the theatrical cut.
-The korean contains a SHORTER director's cut.
I've noticed two cuts (I'm sure there's one or two more), and they're really obvious and awkward:
-Sun-Woo forgetting his car keys at Hee-Soo's place at the end of their first meeting.
-Someone knocking over a chair at the beginning of the cello rehearsal.
+The original music from the final corridor shoot-out has been replaced by an existing track (the scene where Sun-Woo's hand is broken).
Strangely enough, the scenes that have been cut are both funny. It looks like the director decided to remove some humour from the film after its initial release.
As a result the DC is more efficient as an action film, but it lacks character.
(The cello scene becomes much more serious in the DC)
*End of spoilers*
I can't recommend either version because both are different movies.
-If you're looking for a sleek action film, go for the DC.
-If you can handle more light-hearted moments, buy the Tartan.
Note:
I should point out that I saw this movie for the first time a year ago and was EXTREMELY disappointed with it (it was the DC).
But I decided to give it another chance and bought the Tartan. All of a sudden, for no apparent reason, I appreciated it a whole lot more.
The subtle humoristic touches made all the difference IMO.

I used to be "the man who loves the movies you hate".
Now I'm just "that weird french guy with a cat avatar who comes to BnB once a year for no reason and then disappears again".