> If you asked for a novel (less information content than a 512x512 image) from ChatGPT and judged it by how it held together at a high conceptual level relative to output from a stable diffusion image I don't think it would seem that different.

Try asking ChatGPT to write you a novel, chapter by chapter. The chapters may seem okay individually, but you'll find chapter 5 contains statements which completely contradict those in chapter 1. And this can still be true even if ChatGPT is producing chapter 5 based on chapters 1 to 4 as input. (I think ChatGPT could do with some more training and/or engineering on detecting and avoiding contradictions in its output.)

I think one advantage of generating images, is you can notice problems with the output very quickly. With text, you might not notice the contradiction between chapters 1 and 5 until you reread it days later. Similarly, if you get two generated images, and you like bits of both of them, it isn't too hard to edit them together (even roughly) in an image editor, then use further generative techniques to smooth that roughness out. If ChatGPT writes you two different fifth chapters for your novel, and you like bits of both, merging them together can be a more tedious process.