Solo Leveling or "I Alone Level Up" as it is titled in Korea. So when approaching Solo Leveling, the real question is WebNovel or WebComic? Which is the better experience, and does an audiobook version bring anything to the table?
Pricing-wise, published web novel and audiobook end up costing roughly the same price. However, pricing gets weird when it comes to the WebComic; while it is available by volume, it is also free to read legally through Tappy Toon—allowing it to be viewed for free(ish). So it, in reality, comes down to how you want to consume your content and understanding there are variances in the work as the WebComic is an adaptation.

I enjoyed the novel because Sung Jin Woo actually feels human and has a somewhat more human response to the situations he finds himself in. This could be because, for the novel, we exist in his head but rather than a third-party observer.

The webcomic makes him feel more like a generic Isekai protagonist, who honestly seems a lot more willing to kill than his novel counterpart. He also lacks a lot of the compassion we are shown in the novel.

What the webcomic did great instead was the story. Some points honestly spooked me while reading the webcomic that just didn't shine through the same or it at all in the book. In addition, the images and backgrounds allow for a level of worldbuilding that isn't as easy to present in written form.

If I were to narrow it down to one factor on how to pick, I'd say if you are more interested in character development, read or listen to the book. On the other hand, if you care more about the story of Jin Woo and this world, pick up the comic.

A weird note about the novel, and subsequently this audiobook, is that instead of describing something, you WILL get an onomatopoeia instead, just like if you were reading a comic. Which is odd at some points and hilarious at others; one specifically caused me to burst out laughing at work.
But this way of writing is so different that it is easy to understand that it could be more challenging to listen to this book instead of reading it.
I'd say it took me around an hour to acclimate.

Also, if you go looking for more info on this series, be careful. I felt like everywhere I turned held more spoilers for me.