I wanna say both because they're different. But to follow the rules of the topic title.
Movies.
There's a lot of good art out there and movies stimulate and tell stories on multiple levels.
But, the collaborative aspect and corporate need to make a lot of money makes the art form prone to dilution, confusion, or compromise.
A book is generally a pure intimate conversation with the author with some adjustments from editors and publishers. It's slow, it's deep, it begs to live in your mind for days or weeks or months.