I like both them.
WEBTOON's sleek and user friendly. Their audience is massive and they have excellent branding. However I feel like there are much fewer features for indies. Canvas doesn't allow tipping which is disappointing, and you have to have 40,000 monthly page views to earn ad revenue. I occasionally gain subscribers quickly on WEBTOON, but it's unpredictable.
Tapas offers tons of features for indies with ink, ad revenue, and an awesome forum. I feel like it's easier to promote my comic on Tapas internally, vs trying to drive traffic to WEBTOON via 3rd party sites.
I think the reality of the business these days is that if you want to be indie you need to be everywhere.