The storyline for the webtoon is generally the same but there are actually quite a lot of details that's cut out compared to the original manga. Especially the beginning. I prefer the manga of course, there are also moments in the manga that are so damn cute that they didn't include in the webtoon. The only down side to the manga is that the back part wasn't scanned properly so it's like a two page thing going on and you have to zoom in. But honestly I freaking love this manga that I didn't care about that.
Since it was a manga, the original also obviously had more scenes. Like more shots.
In general, if you're going for the story, the manga is better. The webtoon is more like a quick recap for me who read the original before.
The original translation differs from the webtoon, I've read the original several times so this is a problem for me, makes me think I'm crazy because I remember the original so well, but if this is your first time reading this, then maybe start with the webtoon all of the drawings match up pretty well with a few exceptions but for the most part it's the way it's the change in grammar for me...
I don't like that the webtoon change the translation I read this before in the original and so I don't like the fact that they did that they should have kept it the same way and just made it in color don't change things that's annoying