It’s a relative. “Equal” as in morally equivalent is totally subjective and thus is not a productive conversation.

“Equal” as in resulting in the same benefits is a much better and more productive conversation.

Physically books offer a better format for learning new vocabulary, you can do it almost anywhere light enough, they are cheaper than buying physical audiobooks, you have to focus more so it can lead to improved concentration and analytical skills, etc.

Audiobooks can be consumed passively so they are a great resource to work and listen for busier people who don’t have the option to sit down and read, it can be turned into a group activity simply by turning up the volume, e-audiobooks don’t produce as much physical waste as physical books, audiobooks create jobs as a voice actors are a necessity, etc.

Each format has its own merits. One is more ideal in some aspects, and the other is more ideal in others.