To be fair, there are some books that are better as audio books than regular books, and vice versa.
Example A: The Kane Chronicles Trilogy, by Rick Riordan
According to in-story lore, the books have been transcribed from audio messages from Protagonists Carter and Sadie Kane. The two fight over the microphone in the book, and have different styles of narration. The audio books do a good job of conveying this, having both a male voice for Carter's parts, and a female voice for Sadie's parts. This little touch adds a lot of realism to the book that couldn't be achieved through reading.
Example B: The Leviathan Trilogy, by Scott Westerfield
The Leviathan Trilogy also features two main Protagonists, Aleksander and Deryn, with a male voice used for both parts. However, the advantage of the physical version of this book is the addition of illustrations that allow you to properly visualize both the characters and the environment. Obviously the audio book cannot have pictures, making it much more difficult to understand 'see' what is going on.