Yeah, it's not really true that Tapas has more of an issue with audience size compared to number of works than Webtoon. Webtoon has a bigger audience and also more works, but even less space devoted to features, so it can be harder to get seen on.
The main difference between Tapas and Webtoon is you can potentially "beat the system" on webtoon through techniques like saving up a bunch of updates to spam during a canvas event, or making a comic in a small genre like "superhero", so comics that aren't particularly polished or aren't in a trendy genre may well have a bigger readership on Webtoon, especially if they're built around something "high concept" or have a good "elevator pitch" premise. Successful webtoon creators often try cheesy tactics like launching a high concept comic and then dumping it if it's not blown up within the first couple of months and launching a new one.
Tapas meanwhile is a lot more curated and succeeding on Tapas means working within the system, so if you focus on polished presentation and try to make something at least somewhat appealing to the platform's core audience (mostly Women aged around 20), you have good odds of getting seen and boosted by the staff, even if the concept isn't as easy to sell in a few words. Slow and steady growth is more viable on Tapas, even if the numbers generally won't be as huge as a big webtoon (the pay at the top end can still be good though, especially if the work has an engaged audience on Patreon too).
So if we imagine it in print comic terms:
Attack on Titan would do better on Webtoon. The manga was rough looking but with a really punchy story concept and a big opening, and it could go in a genre like Horror or Action and stand out there.
Lumberjanes would do better on Tapas. It's a weird concept to sell, very character-focused and gets going slowly, but with a strong, consistent visual "brand", and the core audience is young women. It would probably go into LGBTQ+ and perform pretty well.