Book gimli is an intelligent, articulate warrior poet.
Film gimli is a bumbling comedic relief.

For example when they enter Moria, in the film, most of the exposition in the film is given to Gandalf, with Gimli being reduced to gasping and awing.

"These are not holes," said Gimli. "This is the great realm and city of the Dwarrowdelf. And of old it was not darksome, but full of light and splendour, as is still remembered in our songs."

He rose and standing in the dark he began to chant in a deep voice, while the echoes ran away into the roof.

Followed by Gimli singing a song about its former splendour

At the tomb of Balin, instead of crying and moaning the whole scene:

"He is dead then," said Frodo. "I feared it was so." Gimli cast his hood over his face.