It's hard to give very specific examples without having access to your source material, but there are a few approaches that might help you compare and contrast the two different forms of media. In trying to evaluate why the director would have chosen to alter a specific part of the...
It's hard to give very specific examples without having access to your source material, but there are a few approaches that might help you compare and contrast the two different forms of media. In trying to evaluate why the director would have chosen to alter a specific part of the original text, think about the differences between reading a book and watching a movie.
First, how are you getting most of your information? When you read a book, all the relevant narrative information is coming to you in one way: words. Words describe what a character looks like, what someone is wearing, what's happening in the environment, what characters are thinking, how they're moving, how their voices sound, and so on. Nothing happens without it being explicitly written down.
In a movie, a director isn't bound to work within the restrictions of text. They can passively provide information in other ways, which allows them some wiggle room to shift conscious focus to parts of the story that they're most interested in. Showing the difference in size between two characters is one relevant example, but they can also use visual and auditory clues to suggest subtler differences—one character's clothes might be a little more worn to suggest a different economic status. Another's voice might be a little weak to suggest feebleness. How might this advantage have driven the director of Gulliver's Travels to make the changes you're seeing between the two interpretations?
There are also some logistical differences between how we experience movies and how we read books. Movies, typically, are fairly short. Even with the added advantages of hearing and seeing, stories often need to be shortened to work well in that format. How might this have limited the director of the movie in choosing what to include?
Additionally, movies are often a social experience, whether you're watching with a few loved ones at home or in a theater full of strangers. Books, by contrast, are typically enjoyed alone. How might this have influenced the choices made by the director?