I am not advocating Kbin or Lemmy. But it is interesting to me that the reason behind the inception of Kbin was related to Lemmy. See the full discussion here where the creator of Kbin, @ernest, stated:

The point is, I don’t want to create a lesser evil here. I want to create something truly good, which is why from the very beginning I’ve been striving to be transparent on all fronts. I’ll just say that before starting from scratch, I tried to create kbin as a fork of Lemmy. I like Rust, I respect them as architects and I’ve learned a lot about managing such a project. However, ultimately, I believe that I cannot remain indifferent to certain things. That’s why kbin is what it is now. Nevertheless, that collaboration with Lemmy’s developers can be beneficial for all of us at this stage. After all, Lemmy is not just one instance, and many amazing people are building the fediverse using this software.

What was those “certain things” we do not know. But the full discussion there revolves around the political views. Check it yourself. But at the end of the day, choose what suits you best since they are contribute to the same Threadiverse.