1.) Tapas & Webtoons
2.)
Tapas:
In 2016 when I was thinking abut getting back into drawing and comic-making I was watching some Youtube videos about comic creation steps and publishing and learned about tapas(tic) that way.
Webtoons:
Word of mouth from these forums. I didn't know it existed prior to hearing people here talk about it.
3.)
Tapas:
Reasonably detailed analytics, scheduling, easily unlockable monetization (ad revenue unlocks account-wide at a relatively low threshold, tipping is a little higher but can be manually unlocked sooner during some special events), has a forum community, ability to place links in episode descriptions, decent customization options for your series page, creator wall, notifications for things related to your series.
Webtoons:
Well known/large potential audience... yeah~
4.)
Tapas:
Small-ish userbase/potential audience, lack of creator wall on app for easy reader notifications
Webtoons:
Lack of customization options, lack of scheduling (until recently I guess, I haven't posted there since it's been implemented), wimpy analytics, lack of notifications relative to your series (no notifs when someone comments makes it very difficult to interact with readers on anything except your most recent episode(s)), difficult monetization thresholds for newer creators, inability to place links in episode descriptions and short character limits as well on said descriptions, lack of creator profile/page/wall.