I watched the series and the movie version side-by-side. Apart from one scene that's not in the series and some minor editing changes, they are identical.
So, if you want to choose, I think the movie is a bit too long to watch it in one sitting (it's easier to find your place again in a series). Forthe series, I found the flashing light and the electric noise at the start of each episode grating, especially when I have a headache.

Things I liked:
* To do an "enemy-to-lovers-trope" is not easy. You can easily draw things out too long or have a power imbalance -- if the relationship reads more as "bullying" than as "mutual antagonism" it's really hard for me to understand how they would ever end up as lovers. (Looking at you, Make Our Days Count) But here, it ends relatively early, both give as good as they get -- and especially Jang Jae Young as the first instigator backs off when he realizes that he's crossed the line.
* I also loved Chu Sang Woo's character, which reads as somewhere on the autism spectrum for me. It's done better that in the original material, imo.
* The supporting characters were great in rounding out the story.

Things I did not like:
* I think I'd have liked to see the discussion about excavators and the subsequent drawing of one on Chu Sangwoo's arm (rather than the ugly veggie thing).



Overall, the pacing was good, and even if the general storyline was predictable (which is par for the course in romance dramas), the journey of both protagonists was lovely to follow.