I have huge gaps all in favor of Tapas. All series are BL.
Going Up
Tapas: 5207 Webtoon: 732 Difference: 4475
2 Men and the Sea
Tapas: 2471 Webtoon: 73 Difference: 2398
The Death and Him
Tapas: 2703 Webtoon: 1639 Difference: 1064
Let me win you [over]
Tapas: 796 Webtoon: 113 Difference: 683
My observations:
I always go by "more updates-> more people see you-> more people probably will follow". This barely works for me on Webtoon. The longest comic is not the one which has more subs on Webtoon.
Updates seem to really mean nothing, "The Death and Him" blew up during some event when (I guess) people had to read certain genre of comics to get coins. But it was a few days only and as you see Tapas already surpassed Webtoon.
Quality and quantity of the comic episodes MEAN NOTHING. Literally. I saw a lot of art and story gems which not even near 1K. And I feel bad for these people... I think I saw a thread on tapas which is 2-3 years old where people share their webtoon links and only 4-5 were still active while others are gone or abandoned never hitting bigger milestones.
*
What it means? To me Webtoon is about luck and how many new readers YOU bring to the platform. Every time I check "Up and coming" it's people with preestablished fan bases (IG, other comics and so on) which get a boost from said fan base and as a reward Webtoon boosts them in "Up and coming" section which is logical for the platform, but hell to see if you don't have a big fan base.
However, there is luck... I was kind of lucky to get "The Death and Him" somehow be in that event for few days. But think about that I have 4 comics, 125 episodes, and ONE TIME I got a shot which was cut off once I started getting close to ad program.
And honestly Webtoon as a platform is depressing for me.
/rant on
On Tapas I feel closer to the readers I see my actions mean something, I see my work being paid off and rewarded even if you say it's small. I give more = I recieve more.
But on Webtoon I get way less than that.
- No comment notifications, I need to manually got through 125 episodes to find new comments. I love my Webtoon readers, why it has to be such a work to connect with them?
- Anyone can come and make my rating go down bc they felt like awarding my comic 1 star is fair.
- I worked my ass off trying to get to ad program, but the result is: take 20k US views after 21 updates and f off, you need 30k, maybe if you make MORE THAN 21 episodes per month you MAYBE will get that 30k US views. And no, you can't say "these 21 episodes were bad, probably", because on Tapas it was the peak of the series as to this day - 124k views, ~10k likes and 540 comments.
I am not a person with much luck - whatever following I got was through WORK. Someone can make an artwork and blew up to 5K followers, I had to make 300+ plus to hit 5k on DA and these artworks honestly I don't consider low effort or bad as people pay me to draw for them so that means my skills are at least good to be paid for. And I accepted it. I accepted that for whatever I do - nothing will be easy for me. I will draw and write day and night, having barely any life in the process. Ok, cool. But I will always feel that whatever I get was earned.
Tapas worked this way for me. And it made me happy.
Webtoon is so luck and pre-popularity-based, the platform is unrewarding. It takes more of me than it gives. 
/rant off
