One difference could be in the editing. Light novels usually go through more professional editing compared to web novels. So, the 'Kumo desu ga Nani ka' light novel might have a more polished writing style.
There are several differences between the web novel and light novel versions of 'Kumo desu ga Nani ka'. Firstly, the light novel often has a more refined presentation with better - quality paper and binding if you have the physical copy. In terms of the story, the light novel may make some adjustments to the plot for better coherence and to fit the overall theme more tightly. For example, some side stories or minor plot points in the web novel might be expanded or cut in the light novel version. Also, as mentioned before, the inclusion of illustrations in the light novel can give readers a different visual understanding of the story's world and characters compared to just reading the text - only web novel.
The light novel of 'Kumo desu ga Nani ka' may have additional illustrations which enhance the reading experience. In terms of content, while the overall story might be the same, there could be some differences in pacing. The web novel might have been updated more frequently in the early stages, leading to a potentially different flow of the story compared to the light novel which is more structured in its release.