I started uploading my comic to both platforms at the same time (and also instagram but on a delay).
I noticed WebToon's discover section gets a decent amount of traffic. If you update multiple times a week you can easily build up an audience of 1k in a week (depends on genre a bit). After about 10 weeks I noticed my numbers stagnate (subscribes and views).
Webtoons is a chore to use unfortunately but its worth it. The audience there can be very dedicated and Im glad I post there too because otherwise would not have had the pleasure of chatting with those folks 
I think Tapas has much better community features though (forums, user pages, events, supporter program). I was featured recently but even before then I managed to steadily acquire a small amount subscribers/views with each update. You can actively reach out to the staff here too. I don't even know where to do that on webtoons? maybe the help pages?
Of course instagram is not a comics platform but it does offer good exposure when done properly. I get dms for comic site suggestion often and I always suggest Tapas because its so much easier to track whats going on here ^^; Also from a management perspective its the best experience Ive had, outside of hosting my own comic's website.