It really depends on different groups of readers. Some hardcore fans who follow the story from the very beginning might prefer the web novel as it has the original and unfiltered content. But generally, the light novel might be more popular among a wider range of readers. It has better presentation with its illustrations and is more widely available in bookstores, which makes it more accessible to casual readers who might not be into the online web novel scene.
The popularity of the Death March web novel and light novel can vary. The light novel has the advantage of being a more mainstream product. It's easier to find in stores, and it has a more polished look. It can attract readers who are interested in the story but also like the aesthetic of a well - produced book. The web novel, on the other hand, may be more popular among a subset of readers who are very engaged with the online writing community. They might enjoy the fact that the web novel can be updated more frequently and they can interact with the author or other fans more directly. But overall, if we look at a broader audience, the light novel is likely to be more popular.