It definitely feels like it's hard to attract new readers through Tapas itself; my memory's fuzzy now but I think when I first posted on Tapas I had maybe six subs for months. Most of the subs that came later came through links advertising from other places. On Webtoon, I only had work up there for about a week, but got like a hundred subs in that time, which seemed incredible in comparison to my experience on Tapas and other platforms just posting something for the first time without an established audience.
(Of course, my comic is a fancomic and after that first week on Webtoon I got notice it had been taken down for apparently copyright infringement, lol. So, my overall impression of Webtoon was that, it has a huge pool of potential readership and strong visibility for new work, but the environment kind of strict creatively speaking, perhaps more geared toward creators looking to make money off their work, and just kind of unfriendly in general. I've tried doing searches to find out if any other fanartists had the same experience, but couldn't find anything, and of course contacting Webtoon help directly isn't going to get a reply.)
Also something I didn't realize about Webtoon until seeing it here, that it doesn't provide notifications for comments--knowing that it's just as well I got kicked off; that just kills any sense of community. (That was one of the many crippling aspects of new Smack Jeeves that helped ensure its demise.) I would choose Tapas as a platform based on that alone.