I think shorter chapters have the advantage that you can easily read the story in between. On a bus or train, for example. 5k chapters need a little longer to read, and it is unsatisfying if you have to stop mid-chapter. The attention span of people is also surprisingly low, so I guess pushing the next chapter button is something that can help people refocus or take a break when needed. On the other hand, if your writing is good and your readers take the time to sit down to enjoy your story, long chapters make the reading experience more immersive. Shorter chapters also increase the visability of your story (assuming you keep up with the word count). Generally, I think a lot depends on your release schedule. If you only release one chapter per week, it might be better to split it in two and release two per week. If you would publish one chapter a day, you wouldn't need to split it (that pace would be insane). If you only release once a month, I would say a longer chapter would be better. I mean, if I wait so long, i at least want to read for more than 5 minutes.