This also depends on your writing skill starting off as well as what your long term goals are. In my case, my rough draft is better than a lot of other writers' second drafts, and I have been told my material is way better than the standard of a lot of these webnovel sites. Having this level of polish in your writing allows you to simply post what you've got as you write it.
Then there's also whether your plan is to just write for a little fun, be a career webnovelist living off patreon/subscribe star donations, or getting yourself published. If you wanna get published, well, getting your material out as you finish it has the real benefit since you get reader feedback as you're going. If your goal is to be a career webnovelist, you are going to want to edit your chapters before posting them wherever you can. If it's just for fun, well, no rules. Do whatever you like.