Depends? You can also copy a book exactly (i.e. word for word, not photocopying), and digital media also deteriorates.

Digital media deteriorates faster in cold storage than a physical book, but is easier to copy.

Properly stored: CDs die anywhere between 10 and 30 years. Some flash drives last 10. Magnetic storage 10-20 years. Books hunders of years.

I’d say physical books are safer against deterioration because it can handle a few generations of “forgetting about it” while a physical copy needs regular backup maintenance.