As a reader: Webtoon wins. It has a much cleaner UI, less invasive ads (I lost the count of how many times I had to quickly close the Tapas app because of awfully loud video ads), all series are available for everyone with no paywalls involved, bookmarks seem to work better overall, finding canvas series is much easier and doesn't feel like I have to jump through a ton of hoops just to find them. Also, recommendations that are actually based on my own genre preferences, omg.
As a creator: Tapas has overall a much more interactive community, better tools for creators (you don't have to schedule episodes in the exact order they're supposed to come out, you can reorder episodes, you get notifications for comments/followers/whatever like you're supposed to, you're free to delete spam/rude/unwanted comments) and makes it much easier to gain a few cents thanks to Ink donations, while the requirements for Webtoon are pretty damn ridiculous. So, as far as the community goes, Tapas definitely wins.
However... Webtoon has a bigger audience, offers better chances for visibility (especially if you post under a small-ish genre) and isn't as narrowly focused on a single genre/style as Tapas seems to be, which, again, means more chances for indie creators who don't fall under a very specific category to get noticed. Granted, manga, fantasy and romance are still pretty big on Webtoon, but they don't seem to be the ONLY genre that is promoted on there... unlike Tapas, which, I'm afraid, lately feels more and more like I stepped into the romance manga section of a comic shop, rather than a platform for indie authors who write a wide range of genres and have tons of different styles. The home page here looks very... homogeneous and to find anything different it really feels like you have to go through a LOT of clicking, something I don't feel when I look at the homepage of Webtoon.
So... not a full win for Webtoon, but not a full win for Tapas either. Both have their advantages and disadvantages.