Biggest difference in audio quality, especially with regards to bass. The best example would be scenes with gunfire like the opening Opera Siege sequence of Tenet or the batmobile chase in Batman (2021).

However not all movies have that big difference - if you have heavy dialogue or if there was little effort put into sound design then you might as well stick to digital.

As a guide, if the sound quality was excellent in the movie theatre then i would put down money for 4k disk.