Smackjeeves honestly has the best format when uploading material, allowing for greater control. You can move chapters around, move episodes around. There's a lot of control overall you have on Smackjeeves but unfortunately, that control means nothing without an audience. The site is very inactive and doesn't have anywhere near the same level of activity as other places.
Frankly, the only reason to use Smackjeeves is as a mirror site, a place to get extra reader attention and bring them over to a proper site. Webtoons is simlar but for other reasons. In this case, Webtoons has honestly one of the worst, most elitists community for a hosting site I've ever seen. The problem with Webtoons is that there is no control as a creator and no community or communication within the site as well. This makes it painfully easy to abuse the system there.
The only reason to use Webtoons is to actively become featured or your work specifically tailors to their demands. Otherwise, use it as a mirror site again but there are better options. Webtoons would be far better if many things were added. For example, there is basically no notification system on LINE an as a creator, you have absolutely no way to deal with unsavory individuals other than a report option which hardly does anything. There's also no community, meaning that its hard to really get in touch with other readers or creators.
Quite frankly, the toxic community of LINE, not helped by the way LINE has the site run, is a huge turn off for me. Also as a creator, I want to build a community and relationship with my readers. I have that kind of control on Tapas but I don't have it on LINE. This is why its not uncommon for people to say they have more "subs" on LINE but less "Interaction."
Out of the three, Tapas is the best one and that's not to say Tapas doesn't have its own issues. However Tapas has a good balance between exposure and creator control and communication. It's mature, friendly and gives you enough options to work with.